commit 27d238cbe6b7181f61db7edfc19c747ef4c75f6f
Author: emil28092005 <emil28092005@gmail.com>
Date:   Fri Oct 30 19:56:16 2026 +0300

    Ice slab with layered plasma, two-pass refraction
    
    Pass 1 renders eight plasma sheets into an atlas with linear depth in alpha;
    pass 2 marches the refracted ray to each sheet and absorbs it by real path
    length, so near and far layers separate under pointer parallax. Plasma cycle
    repeats exactly every 30 s; - / = change speed.

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..7a60b85
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+__pycache__/
+*.pyc
diff --git a/1_plasma.frag b/1_plasma.frag
new file mode 100644
index 0000000..75f18f7
--- /dev/null
+++ b/1_plasma.frag
@@ -0,0 +1,18 @@
+precision highp float;
+uniform vec2 u_res; uniform float u_time; uniform vec2 u_mouse;
+float hash(vec2 p){return fract(sin(dot(p,vec2(127.1,311.7)))*43758.5453);}
+float noise(vec2 p){vec2 i=floor(p),f=fract(p);f=f*f*(3.0-2.0*f);
+ return mix(mix(hash(i),hash(i+vec2(1,0)),f.x),mix(hash(i+vec2(0,1)),hash(i+vec2(1,1)),f.x),f.y);}
+float fbm(vec2 p){float a=0.5,s=0.0;for(int i=0;i<5;i++){s+=a*noise(p);p*=2.03;a*=0.5;}return s;}
+void main(){
+ vec2 p=(gl_FragCoord.xy-0.5*u_res)/u_res.y;
+ float t=u_time*0.15;
+ vec2 q=vec2(fbm(p*2.0+vec2(0.0,t)),fbm(p*2.0+vec2(5.2,-t)));
+ vec2 r=vec2(fbm(p*2.0+q*1.8+vec2(1.7,9.2)+t*1.3),fbm(p*2.0+q*1.8+vec2(8.3,2.8)-t*1.1));
+ float v=fbm(p*2.0+r*2.2);
+ vec3 col=mix(vec3(0.02,0.03,0.10),vec3(0.85,0.25,0.35),smoothstep(0.2,0.9,v));
+ col=mix(col,vec3(0.15,0.65,0.95),smoothstep(0.5,1.0,length(r-0.5)));
+ col+=0.35*pow(max(0.0,1.0-length(p*0.9)),3.0)*vec3(1.0,0.85,0.6);
+ col*=1.0-0.5*length(p)*0.4;
+ gl_FragColor=vec4(col,1.0);
+}
diff --git a/2_tunnel.frag b/2_tunnel.frag
new file mode 100644
index 0000000..2dda318
--- /dev/null
+++ b/2_tunnel.frag
@@ -0,0 +1,17 @@
+precision highp float;
+uniform vec2 u_res; uniform float u_time; uniform vec2 u_mouse;
+void main(){
+ vec2 p=(gl_FragCoord.xy-0.5*u_res)/u_res.y;
+ float t=u_time*0.6;
+ float a=atan(p.y,p.x);
+ float r=length(p)+0.001;
+ float z=1.0/r+t;
+ float rings=fract(z*2.0+a*0.6+sin(a*3.0+t)*0.3);
+ vec3 base=mix(vec3(1.0,0.15,0.55),vec3(0.15,0.9,1.0),smoothstep(0.0,1.0,rings));
+ float glow=pow(1.0-r,2.0);
+ float band=smoothstep(0.45,0.5,rings)*smoothstep(0.6,0.5,rings);
+ vec3 col=base*band*glow*2.2;
+ col+=vec3(0.9,0.5,1.0)*pow(glow,8.0)*1.5;
+ col+=0.02*vec3(0.3,0.1,0.5)/(r*r);
+ gl_FragColor=vec4(col,1.0);
+}
diff --git a/3_orb.frag b/3_orb.frag
new file mode 100644
index 0000000..5215d2a
--- /dev/null
+++ b/3_orb.frag
@@ -0,0 +1,38 @@
+precision highp float;
+uniform vec2 u_res; uniform float u_time; uniform vec2 u_mouse;
+float sdSphere(vec3 p,float r){return length(p)-r;}
+float map(vec3 p){
+ float d=sdSphere(p,1.0);
+ for(int i=0;i<3;i++){
+  float fi=float(i);
+  vec3 q=p; float a=u_time*0.5+fi*2.1;
+  q.xz=mat2(cos(a),-sin(a),sin(a),cos(a))*q.xz;
+  d=min(d,sdSphere(q-vec3(0.75,0.0,0.0),0.34));
+ }
+ return d;
+}
+void main(){
+ vec2 uv=(gl_FragCoord.xy-0.5*u_res)/u_res.y;
+ vec3 ro=vec3(0.0,0.0,3.6), rd=normalize(vec3(uv,-1.6));
+ float tt=0.0; int hit=0;
+ for(int i=0;i<80;i++){
+  float d=map(ro+rd*tt);
+  if(d<0.001){hit=1;break;}
+  tt+=d;
+  if(tt>8.0)break;
+ }
+ vec3 col=vec3(0.03,0.04,0.07)+0.15*pow(1.0-abs(uv.y),3.0);
+ if(hit==1){
+  vec3 pos=ro+rd*tt;
+  vec3 n=normalize(vec3(map(pos+vec3(0.001,0,0))-map(pos-vec3(0.001,0,0)),
+                        map(pos+vec3(0,0.001,0))-map(pos-vec3(0,0.001,0)),
+                        map(pos+vec3(0,0,0.001))-map(pos-vec3(0,0,0.001))));
+  vec3 l=normalize(vec3(0.6,0.8,0.5));
+  float dif=max(dot(n,l),0.0);
+  float fre=pow(1.0-max(dot(n,-rd),0.0),3.0);
+  vec3 alb=0.5+0.5*cos(6.2831*(pos*0.6+vec3(0.0,0.33,0.67)));
+  col=alb*(0.15+0.85*dif)+vec3(0.6,0.8,1.0)*fre*1.2;
+  col*=0.9+0.1*sin(pos.y*40.0+u_time*4.0);
+ }
+ gl_FragColor=vec4(pow(col,vec3(0.4545)),1.0);
+}
diff --git a/4_ice_scene.frag b/4_ice_scene.frag
new file mode 100644
index 0000000..27efc81
--- /dev/null
+++ b/4_ice_scene.frag
@@ -0,0 +1,56 @@
+// Pass A: icy scene. RGB = colour, A = linear depth / 8.0  (our z-buffer)
+precision highp float;
+uniform vec2 u_res; uniform float u_time; uniform vec2 u_mouse;
+
+float sdSphere(vec3 p, float r){ return length(p) - r; }
+
+float map(vec3 p){
+  float d = sdSphere(p, 1.0);
+  for(int i=0;i<3;i++){
+    float fi = float(i);
+    vec3 q = p;
+    float a = u_time*0.5 + fi*2.1;
+    q.xz = mat2(cos(a),-sin(a),sin(a),cos(a)) * q.xz;
+    d = min(d, sdSphere(q - vec3(0.75,0.0,0.0), 0.34));
+  }
+  return d;
+}
+
+void main(){
+  vec2 uv = (gl_FragCoord.xy - 0.5*u_res)/u_res.y;
+  vec3 ro = vec3(0.0,0.0,8.5);
+  vec3 rd = normalize(vec3(uv, -1.6));
+
+  float t = 0.0; int hit = 0;
+  for(int i=0;i<90;i++){
+    float d = map(ro + rd*t);
+    if(d < 0.001){ hit = 1; break; }
+    t += d;
+    if(t > 12.0) break;
+  }
+
+  vec3 col = vec3(0.008,0.02,0.045);
+  col += 0.07*pow(1.0 - abs(uv.y)*0.9, 4.0)*vec3(0.15,0.35,0.6);   // cold haze
+  float depth = 12.0;
+
+  if(hit == 1){
+    depth = t;
+    vec3 pos = ro + rd*t;
+    vec3 n = normalize(vec3(map(pos+vec3(0.001,0,0))-map(pos-vec3(0.001,0,0)),
+                            map(pos+vec3(0,0.001,0))-map(pos-vec3(0,0.001,0)),
+                            map(pos+vec3(0,0,0.001))-map(pos-vec3(0,0,0.001))));
+    vec3 l = normalize(vec3(0.45,0.85,0.55));
+    float dif = max(dot(n,l),0.0);
+    float fre = pow(1.0 - max(dot(n,-rd),0.0), 3.0);
+
+    // frozen layers instead of rainbow
+    float f = 0.5 + 0.5*sin(pos.y*20.0 + u_time*2.0 + pos.x*5.0 + n.z*3.0);
+    vec3 alb = mix(vec3(0.90,0.97,1.00), vec3(0.34,0.66,0.92), f);
+    col = alb*(0.06 + 1.05*dif) + vec3(0.60,0.90,1.0)*fre*1.6;
+    col *= 0.86 + 0.14*sin(pos.y*38.0 + u_time*4.0);
+  }
+
+  // depth fog: far things fade into the cold void
+  col = mix(col, vec3(0.03,0.10,0.19), smoothstep(3.0, 12.0, depth)*0.85);
+  gl_FragColor = vec4(col, clamp(depth/12.0, 0.0, 1.0));
+}
diff --git a/5_ice_refract.frag b/5_ice_refract.frag
new file mode 100644
index 0000000..4bac8d6
--- /dev/null
+++ b/5_ice_refract.frag
@@ -0,0 +1,107 @@
+// Pass B: the ice wall. Refracts pass A through a displaced surface using its depth buffer.
+precision highp float;
+uniform vec2 u_res; uniform float u_time; uniform vec2 u_mouse;
+uniform sampler2D u_scene;
+
+const float ICE_Z = 1.20;      // front face of the ice
+const vec3  SIG_A = vec3(0.13,0.042,0.020);  // absorption in ice (red dies first -> blue)
+const vec3  SIG_B = vec3(0.16,0.055,0.026);  // absorption in the "depth fog" behind
+
+float hash(vec2 p){ return fract(sin(dot(p,vec2(127.1,311.7)))*43758.5453); }
+float noise(vec2 p){
+  vec2 i=floor(p), f=fract(p); f=f*f*(3.0-2.0*f);
+  return mix(mix(hash(i),hash(i+vec2(1,0)),f.x), mix(hash(i+vec2(0,1)),hash(i+vec2(1,1)),f.x), f.y);
+}
+float fbm(vec2 p){
+  float a=0.5, s=0.0;
+  for(int i=0;i<5;i++){ s+=a*noise(p); p*=2.02; a*=0.5; }
+  return s;
+}
+
+// height of the ice surface at (x,y) — almost frozen, drifts very slowly
+float surf(vec2 p){
+  float t = u_time*0.04;
+  return 0.055*fbm(p*1.7 + vec2(t,-t)) + 0.022*fbm(p*4.3 - vec2(t*1.7,t));
+}
+
+vec3 surfaceNormal(vec2 p){
+  float e = 0.004;
+  float hx = surf(p+vec2(e,0.0)) - surf(p-vec2(e,0.0));
+  float hy = surf(p+vec2(0.0,e)) - surf(p-vec2(0.0,e));
+  return normalize(vec3(-hx/(2.0*e), -hy/(2.0*e), 1.0));
+}
+
+// project a world point with the scene camera (ro=(0,0,3.6), fov via 1.6)
+vec2 project(vec3 p){
+  vec3 d = p - vec3(0.0,0.0,8.5);
+  return d.xy/(-d.z)*1.6;
+}
+
+void main(){
+  vec2 uv = (gl_FragCoord.xy - 0.5*u_res)/u_res.y;
+  vec3 ro = vec3(0.0,0.0,3.6);
+  vec3 rd = normalize(vec3(uv, -1.6));
+
+  // --- front surface: plane z=ICE_Z displaced by surf(), two fixed-point steps
+  float t = (ICE_Z - ro.z)/rd.z;
+  for(int i=0;i<2;i++){
+    vec3 p0 = ro + rd*t;
+    t = (ICE_Z + surf(p0.xy) - ro.z)/rd.z;
+  }
+  vec3 ps = ro + rd*t;
+  vec3 n  = surfaceNormal(ps.xy);
+  if(dot(n,-rd) < 0.0) n = -n;
+
+  float cosi = clamp(dot(n,-rd), 0.0, 1.0);
+  float fres = 0.025 + 0.975*pow(1.0 - cosi, 5.0);
+  vec3 sky = mix(vec3(0.015,0.05,0.10), vec3(0.42,0.68,0.98), smoothstep(-0.35,0.95,n.y));
+  sky += vec3(0.9,0.97,1.0)*pow(cosi, 60.0);                      // specular glint
+
+  // --- refraction with chromatic dispersion down to the back face
+  float backZ = ICE_Z - (0.55 + 0.18*fbm(ps.xy*0.9));
+  vec3 sceneCol = vec3(0.0);
+  float pathIce = 0.0;
+  for(int c=0;c<3;c++){
+    float ior = 1.31 + float(c)*0.022;                            // 1.31 .. 1.354
+    vec3 d2 = refract(rd, n, 1.0/ior);
+    if(length(d2) < 0.5) d2 = rd;                                  // total internal reflection guard
+    float t2 = (backZ - ps.z)/d2.z;
+    vec3 pe = ps + d2*t2;
+    pathIce = t2;
+    vec2 suv = project(pe);
+    vec2 texUV = (suv*u_res.y + 0.5*u_res)/u_res;
+    vec4 s = texture2D(u_scene, clamp(texUV, vec2(0.001), vec2(0.999)));
+    sceneCol[c] = s[c];
+  }
+
+  // --- z-buffer: how much ice/fog the view ray had to cross to the object
+  vec2  baseUV = gl_FragCoord.xy/u_res;
+  float dScene = texture2D(u_scene, baseUV).a * 12.0;               // linear depth from pass A
+  float cell   = max(0.0, dScene - (t + pathIce));                 // ice-to-object gap
+  vec3  absorbA = exp(-SIG_A*pathIce);                             // inside the slab
+  vec3  absorbB = exp(-SIG_B*cell);                                // depth haze behind it
+
+  vec3 iceTint = vec3(0.80,0.94,1.0);                              // pure, clean blue ice
+  vec3 col = sceneCol * 1.10 * absorbA * absorbB * iceTint;
+
+  // --- body detail: small trapped bubbles, hair cracks, frozen sheets (static, they live in the slab)
+  vec2 q = ps.xy*2.2;
+  float zone = smoothstep(0.42, 0.62, fbm(q*0.7 + 21.0));          // clear ice vs bubbly ice
+  float bub = noise(q*19.0 + 3.1) * noise(q*17.0 - 1.7);
+  float dots = smoothstep(0.045, 0.075, bub) * mix(0.10, 1.0, zone) * 0.34;
+  float rid  = abs(fbm(q*1.9 + 11.0)*2.0 - 1.0);
+  float crack = smoothstep(0.022, 0.0, rid) * 0.45;
+  float sheet = smoothstep(0.62, 0.78, fbm(vec2(q.y*1.3, q.x*0.35)) );
+
+  float streak = smoothstep(0.55,0.95, fbm(vec2(q.x*7.0, q.y*0.35) + 5.0));
+  float sheen  = pow(max(0.0, dot(n, normalize(vec3(0.35,0.75,0.55)))), 40.0);
+  col += iceTint * (dots + crack*0.22 + streak*0.05 + sheen*0.5) * (0.25 + 0.75*cosi);
+  col += iceTint * sheet * 0.06 * smoothstep(0.0, 1.2, cell);
+
+  // --- reflection on top, thicker rim where the slab turns away
+  col = mix(col, sky, fres*0.85);
+  col += iceTint * pow(1.0 - cosi, 2.0) * 0.10;                    // frosted grazing edge
+
+  col = pow(clamp(col, 0.0, 1.0), vec3(0.4545));
+  gl_FragColor = vec4(col, 1.0);
+}
diff --git a/6_ice_plasma.frag b/6_ice_plasma.frag
new file mode 100644
index 0000000..49f7730
--- /dev/null
+++ b/6_ice_plasma.frag
@@ -0,0 +1,75 @@
+// Pass 1: eight plasma sheets, one atlas tile each. Alpha stores linear depth.
+// Density field lit as a height surface: billowing volumes with a real terminator.
+precision highp float;
+uniform vec2 u_res; // size of one tile
+uniform float u_time;
+
+float hash(vec2 p) { return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453); }
+float noise(vec2 p) {
+  vec2 i = floor(p), f = fract(p);
+  f = f*f*(3.0-2.0*f);
+  return mix(mix(hash(i), hash(i+vec2(1.0,0.0)), f.x),
+             mix(hash(i+vec2(0.0,1.0)), hash(i+vec2(1.0,1.0)), f.x), f.y);
+}
+float fbm(vec2 p) {
+  float sum = 0.0, amp = 0.5;
+  for (int i = 0; i < 4; i++) {
+    sum += amp * noise(p);
+    p = mat2(1.62, 1.17, -1.17, 1.62) * p;
+    amp *= 0.5;
+  }
+  return sum;
+}
+float fbm2(vec2 p) {
+  return 0.5 * noise(p) + 0.25 * noise(mat2(1.62, 1.17, -1.17, 1.62) * p);
+}
+const float EXTENT = 3.8; // half-width of a sheet in world units; must match the ice pass
+
+void main() {
+  vec2 tile = floor(gl_FragCoord.xy / u_res);
+  float layer = tile.x + tile.y * 4.0;
+  vec2 uv = fract(gl_FragCoord.xy / u_res);
+  vec2 p = (uv - 0.5) * 2.0 * vec2(EXTENT * u_res.x / u_res.y, EXTENT);
+  p *= 0.85 + 0.10 * layer; // far sheets carry finer detail, which reads as distance
+  float angle = hash(vec2(layer, 3.1)) * 6.2831853;
+  p = mat2(cos(angle), sin(angle), -sin(angle), cos(angle)) * p;
+
+  // Periodic time: every field returns exactly after 30 seconds.
+  float phase = u_time * 6.2831853 / 30.0;
+  vec2 o = vec2(cos(phase), sin(phase));
+  vec2 seed = vec2(layer * 17.3, layer * 9.1);
+
+  // Two nested warp stages, the marbled-plasma motion.
+  vec2 q = vec2(fbm(p * 0.50 + seed + o * 0.55),
+                fbm(p * 0.50 + seed + 23.1 - o * 0.55));
+  vec2 r = vec2(fbm(p * 0.85 + 2.0 * q + seed + vec2(o.y, -o.x) * 0.40),
+                fbm(p * 0.85 + 2.0 * q + seed + 31.7 - vec2(o.y, -o.x) * 0.40));
+  vec2 w = p * 1.10 + 2.6 * r + seed;   // warped coords of the density field
+
+  // The silhouette is shared by all sheets (slid a little per depth), so the gaps
+  // stay open right through the stack instead of filling in with overlap.
+  float mass = smoothstep(0.520, 0.548, fbm((p + o * 0.30 + vec2(0.10, -0.07) * layer) * 0.62 + r * 1.1 + 13.7));
+
+  // Light the density as a height surface: $cheap 2-octave gradient, strong terminator.
+  float h = 0.05;
+  vec2 slope = vec2(fbm2(w + vec2(h, 0.0)) - fbm2(w - vec2(h, 0.0)),
+                    fbm2(w + vec2(0.0, h)) - fbm2(w - vec2(0.0, h))) * (10.0 / (2.0 * h));
+  vec3 nrm = normalize(vec3(-slope, 1.0));
+  float lit = clamp(dot(nrm, normalize(vec3(-0.38, 0.52, 0.76))), 0.0, 1.0);
+
+  // Folded planes across the volume, feathered so they never read as a grid.
+  vec2 g = (p + r * 2.0) * 1.4;
+  vec2 cell = floor(g), f = fract(g);
+  float feather = smoothstep(0.0, 0.10, min(min(f.x, 1.0 - f.x), min(f.y, 1.0 - f.y)));
+  float facet = mix(1.0, mix(0.70, 1.25, hash(cell + seed + step(1.0, f.x + f.y) * 37.0)), feather);
+
+  float shade = 0.60 + 0.55 * lit;                      // soft light across the folded planes
+  float e = mass * facet * shade * 0.075
+          + mass * (1.0 - mass) * 4.0 * 0.015           // thin torn silhouette
+          + mass * pow(lit, 14.0) * 0.045;              // glint where a fold faces the light
+  vec3 col = e * mix(vec3(0.02, 0.42, 0.60), vec3(0.08, 0.64, 0.88), facet * 0.5);
+  // Faint dye in the open gaps so darkness reads as depth, not as a hole.
+  col += smoothstep(0.40, 0.85, fbm(p * 0.30 + seed * 0.4 + o * 0.3)) * vec3(0.0001, 0.0004, 0.0006);
+
+  gl_FragColor = vec4(col, (0.42 + layer * 0.26) / 2.6);
+}
diff --git a/7_ice_over.frag b/7_ice_over.frag
new file mode 100644
index 0000000..615fc44
--- /dev/null
+++ b/7_ice_over.frag
@@ -0,0 +1,94 @@
+// Pass 2: clean ice. Refraction, chromatic shear, absorption by true path length.
+// Nothing is added to empty space, so the gaps between sheets stay black.
+precision highp float;
+uniform vec2 u_res;
+uniform float u_time;
+uniform vec2 u_mouse; // normalized, bottom-left origin
+uniform sampler2D u_scene;
+uniform vec2 u_tile_res;
+
+const float EXTENT = 3.8;                 // must match the plasma pass
+const float FRONT  = -2.0;                // ice surface, camera at the origin looking down -z
+const vec3  SIGMA  = vec3(0.66, 0.26, 0.11); // absorption per unit: red dies first, so depth turns blue
+const float IOR    = 1.31;
+
+float hash(vec2 p) { return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453); }
+float noise(vec2 p) {
+  vec2 i = floor(p), f = fract(p);
+  f = f*f*(3.0-2.0*f);
+  return mix(mix(hash(i), hash(i+vec2(1.0,0.0)), f.x),
+             mix(hash(i+vec2(0.0,1.0)), hash(i+vec2(1.0,1.0)), f.x), f.y);
+}
+float fbm(vec2 p) {
+  float sum = 0.0, amp = 0.5;
+  for (int i = 0; i < 3; i++) { sum += amp * noise(p); p = mat2(1.62, 1.17, -1.17, 1.62) * p; amp *= 0.5; }
+  return sum;
+}
+vec2 atlasUV(vec2 world, float layer) {
+  vec2 uv = world / (2.0 * EXTENT) + 0.5;
+  uv = clamp(uv, 0.5 / u_tile_res, 1.0 - 0.5 / u_tile_res); // keep bilinear taps inside the tile
+  return (vec2(mod(layer, 4.0), floor(layer / 4.0)) + uv) / vec2(4.0, 2.0);
+}
+// Smooth frozen surface: two octaves, no bubbles, no grain.
+float height(vec2 x) {
+  return 0.22 * fbm(x * 0.85 + 2.0) + 0.06 * fbm(x * 2.6 - 5.0);
+}
+void main() {
+  vec2 screen = gl_FragCoord.xy / u_res;
+  vec2 p = (gl_FragCoord.xy - 0.5 * u_res) / u_res.y;
+  vec2 look = clamp(u_mouse - 0.5, -0.35, 0.35); // orbiting the slab centre
+  vec3 ray = normalize(vec3(p - look * 2.2, -1.6));
+
+  // Front surface along the view ray; two fixed-point steps settle on the swell.
+  float t = FRONT / ray.z;
+  for (int i = 0; i < 2; i++) t = (FRONT + height(ray.xy * t)) / ray.z;
+  vec3 hit = ray * t;
+
+  float e = 0.02;
+  vec2 slope = vec2(height(hit.xy + vec2(e, 0.0)) - height(hit.xy - vec2(e, 0.0)),
+                    height(hit.xy + vec2(0.0, e)) - height(hit.xy - vec2(0.0, e))) / (2.0 * e);
+  float bevel = smoothstep(0.14, 0.0, min(min(screen.x, 1.0 - screen.x), min(screen.y, 1.0 - screen.y)));
+  slope += bevel * (screen - 0.5) * 0.55; // the slab turns away at the frame edge
+  vec3 normal = normalize(vec3(-slope, 1.0));
+  float facing = max(dot(-ray, normal), 0.0);
+
+  // Refracted ray; red and blue bend a little differently, which is what makes ice ring.
+  vec3 inside = refract(ray, normal, 1.0 / IOR);
+  vec2 shearR = (refract(ray, normal, 1.0 / (IOR - 0.012)) - inside).xy;
+  vec2 shearB = (refract(ray, normal, 1.0 / (IOR + 0.016)) - inside).xy;
+  inside = normalize(inside);
+  if (inside.z > -0.05) inside = vec3(0.0, 0.0, -1.0);
+
+  // Recentre the parallax on the middle of the sheet stack: near and far sheets
+  // then slide past each other at different rates as the pointer moves.
+  vec2 par = look * 4.54;
+
+  vec3 acc = vec3(0.0);
+  float trans = 1.0;
+  for (int i = 0; i < 8; i++) {
+    float layer = float(i);
+    float depth = texture2D(u_scene, atlasUV(hit.xy + par, layer)).a * 2.6; // depth buffer from pass 1
+    float path = (hit.z - (FRONT - depth)) / -inside.z;                     // ice crossed to reach this sheet
+    vec2 at = (hit + inside * path).xy + par;
+    vec3 plasma;
+    plasma.r = texture2D(u_scene, atlasUV(at + shearR * path, layer)).r;
+    plasma.g = texture2D(u_scene, atlasUV(at, layer)).g;
+    plasma.b = texture2D(u_scene, atlasUV(at + shearB * path, layer)).b;
+    vec3 c = plasma * exp(-SIGMA * path);
+    // Near plumes are nearly opaque, so the sheets behind them show through the gaps
+    // instead of averaging into a wash. That is what makes the stack read as depth.
+    float alpha = clamp(max(max(c.r, c.g), c.b) * 1.8, 0.0, 0.80);
+    acc += trans * c;
+    trans *= 1.0 - alpha;
+  }
+
+  // Gentle shoulder: overlapping glow stays coloured instead of clipping to white.
+  vec3 col = vec3(1.0) - exp(-acc * 1.5);
+
+  // Glass: reflection and a rim only where the surface turns away. Empty space stays dark.
+  float fresnel = pow(1.0 - facing, 5.0);
+  vec3 sky = mix(vec3(0.004, 0.016, 0.030), vec3(0.075, 0.220, 0.320), normal.y * 0.5 + 0.5);
+  col += sky * (fresnel * 1.2 + bevel * 0.03);
+
+  gl_FragColor = vec4(pow(clamp(col, 0.0, 1.0), vec3(0.4545)), 1.0);
+}
diff --git a/build.py b/build.py
new file mode 100644
index 0000000..9a9e5be
--- /dev/null
+++ b/build.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+"""Inline every *.frag next to this file into playground.html (keys 1..N switch, mouse = u_mouse)."""
+import glob, json, os
+
+here = os.path.dirname(os.path.abspath(__file__))
+frags = sorted(glob.glob(os.path.join(here, "*.frag")))
+names = [os.path.basename(f)[:-5] for f in frags]
+srcs = [open(f).read() for f in frags]
+
+html = """<!doctype html><html><head><meta charset=utf-8><title>shaders</title>
+<style>html,body{margin:0;height:100%;background:#000;overflow:hidden}
+canvas{display:block;width:100vw;height:100vh}
+#osd{position:fixed;left:14px;bottom:12px;font:13px ui-monospace,monospace;color:#9bf;opacity:.75;pointer-events:none}</style>
+</head><body><canvas id=c></canvas><div id=osd></div><script>
+const SHADERS = __SHADERS__;
+const NAMES = __NAMES__;
+const VS='attribute vec2 p;void main(){gl_Position=vec4(p,0,1);}';
+const c=document.getElementById('c'),osd=document.getElementById('osd');
+const gl=c.getContext('webgl',{antialias:false,preserveDrawingBuffer:false});
+let progs=[],cur=0,mx=0.5,my=0.5,t0=performance.now();
+function sh(t,s){const o=gl.createShader(t);gl.shaderSource(o,s);gl.compileShader(o);
+ if(!gl.getShaderParameter(o,gl.COMPILE_STATUS)){osd.textContent='compile error: '+gl.getShaderInfoLog(o);console.error(gl.getShaderInfoLog(o));}
+ return o;}
+for(const s of SHADERS){const pr=gl.createProgram();
+ gl.attachShader(pr,sh(gl.VERTEX_SHADER,VS));gl.attachShader(pr,sh(gl.FRAGMENT_SHADER,s));
+ gl.linkProgram(pr);progs.push(pr);}
+const b=gl.createBuffer();gl.bindBuffer(gl.ARRAY_BUFFER,b);
+gl.bufferData(gl.ARRAY_BUFFER,new Float32Array([-1,-1,1,-1,-1,1,1,1]),gl.STATIC_DRAW);
+function resize(){const d=devicePixelRatio||1;c.width=innerWidth*d;c.height=innerHeight*d;}
+addEventListener('resize',resize);resize();
+addEventListener('mousemove',e=>{mx=e.clientX/innerWidth;my=1-e.clientY/innerHeight;});
+addEventListener('keydown',e=>{if(e.key>='1'&&e.key<=String(progs.length)){cur=+e.key-1;}});
+function frame(){
+ const pr=progs[cur];gl.useProgram(pr);
+ const l=gl.getAttribLocation(pr,'p');gl.enableVertexAttribArray(l);
+ gl.vertexAttribPointer(l,2,gl.FLOAT,false,0,0);
+ gl.uniform2f(gl.getUniformLocation(pr,'u_res'),c.width,c.height);
+ gl.uniform1f(gl.getUniformLocation(pr,'u_time'),(performance.now()-t0)/1000);
+ gl.uniform2f(gl.getUniformLocation(pr,'u_mouse'),mx,my);
+ gl.viewport(0,0,c.width,c.height);gl.drawArrays(gl.TRIANGLE_STRIP,0,4);
+ osd.textContent=NAMES[cur]+'  ['+(cur+1)+'/'+progs.length+']  ·  keys 1-'+progs.length+' switch · move mouse';
+ requestAnimationFrame(frame);
+}
+frame();
+</script></body></html>
+"""
+out = html.replace("__SHADERS__", json.dumps(srcs)).replace("__NAMES__", json.dumps(names))
+open(os.path.join(here, "playground.html"), "w").write(out)
+print("playground.html:", ", ".join(names))
diff --git a/build_ice.py b/build_ice.py
new file mode 100644
index 0000000..371aab8
--- /dev/null
+++ b/build_ice.py
@@ -0,0 +1,116 @@
+#!/usr/bin/env python3
+"""Two-pass ice pipeline: scene -> texture(+depth in alpha) -> refraction -> screen.
+Writes ice.html. Open ice.html#shot&t=2 for a single still frame."""
+import json, os
+
+here = os.path.dirname(os.path.abspath(__file__))
+import sys
+a = sys.argv[1:]
+scene_f, ice_f, out_f = (a + ["4_ice_scene.frag", "5_ice_refract.frag", "ice.html"])[:3]
+scene = open(os.path.join(here, scene_f)).read()
+ice   = open(os.path.join(here, ice_f)).read()
+
+HTML = """<!doctype html><html><head><meta charset=utf-8><title>ice</title>
+<style>html,body{margin:0;height:100%;background:#000;overflow:hidden}
+canvas{display:block;width:100vw;height:100vh}
+#osd{position:fixed;left:14px;bottom:12px;font:13px ui-monospace,monospace;color:#9cf;opacity:.7;pointer-events:none}</style>
+</head><body><canvas id=c></canvas><div id=osd></div><script>
+const FRAG_A = atob('__SCENE_B64__');
+const FRAG_B = atob('__ICE_B64__');
+const VS = 'attribute vec2 p;void main(){gl_Position=vec4(p,0,1);}';
+const SHOT = location.hash.indexOf('shot') >= 0;
+const T = parseFloat((location.hash.match(/t=([\\d.]+)/)||[0,0])[1]) || 0;
+const cv = document.getElementById('c'), osd = document.getElementById('osd');
+const gl = cv.getContext('webgl', {antialias:false, preserveDrawingBuffer:SHOT});
+
+function prog(vs, fs){
+  const sh=(t,s)=>{const o=gl.createShader(t);gl.shaderSource(o,s);gl.compileShader(o);
+    if(!gl.getShaderParameter(o,gl.COMPILE_STATUS)) throw new Error(gl.getShaderInfoLog(o)); return o;};
+  const p=gl.createProgram();
+  gl.attachShader(p,sh(gl.VERTEX_SHADER,vs)); gl.attachShader(p,sh(gl.FRAGMENT_SHADER,fs));
+  gl.linkProgram(p); if(!gl.getProgramParameter(p,gl.LINK_STATUS)) throw new Error(gl.getProgramInfoLog(p));
+  return p;
+}
+let PA, PB;
+try { PA = prog(VS, FRAG_A); PB = prog(VS, FRAG_B); }
+catch(e){ osd.textContent = 'shader error: ' + e.message; document.title = 'ERR'; }
+
+const buf = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1,-1,1,-1,-1,1,1,1]), gl.STATIC_DRAW);
+
+// offscreen target: colour + depth packed into alpha
+let fbo, tex;
+function resize(){
+  const d = SHOT ? 1 : (devicePixelRatio||1);
+  const W = SHOT ? parseInt(location.hash.match(/w=(\\d+)/)?.[1]||700) : Math.round(innerWidth*d);
+  const H = SHOT ? W : Math.round(innerHeight*d);
+  cv.width=W; cv.height=H; cv.style.width = SHOT ? W+'px' : '100vw'; cv.style.height = SHOT ? H+'px' : '100vh';
+  tex = gl.createTexture();
+  gl.bindTexture(gl.TEXTURE_2D, tex);
+  gl.texImage2D(gl.TEXTURE_2D,0,gl.RGBA,W,H,0,gl.RGBA,gl.UNSIGNED_BYTE,null);
+  gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_MIN_FILTER,gl.LINEAR);
+  gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_MAG_FILTER,gl.LINEAR);
+  gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_WRAP_S,gl.CLAMP_TO_EDGE);
+  gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_WRAP_T,gl.CLAMP_TO_EDGE);
+  fbo = gl.createFramebuffer();
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+  gl.framebufferTexture2D(gl.FRAMEBUFFER,gl.COLOR_ATTACHMENT0,gl.TEXTURE_2D,tex,0);
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+}
+resize();
+
+let mx=0.5, my=0.5, speed=1.0;
+if(!SHOT){
+  addEventListener('keydown', e=>{
+    if(e.key==='-'||e.key==='_') speed = Math.max(0.125, speed/2);
+    if(e.key==='='||e.key==='+') speed = Math.min(4.0, speed*2);
+  });
+  addEventListener('resize', resize);
+  addEventListener('mousemove', e=>{ mx=e.clientX/innerWidth; my=1-e.clientY/innerHeight; });
+}
+
+function draw(p, time){
+  gl.useProgram(p);
+  const l = gl.getAttribLocation(p,'p');
+  gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+  gl.enableVertexAttribArray(l); gl.vertexAttribPointer(l,2,gl.FLOAT,false,0,0);
+  const u = n => gl.getUniformLocation(p,n);
+  if(u('u_res'))  gl.uniform2f(u('u_res'), cv.width, cv.height);
+  if(u('u_time')) gl.uniform1f(u('u_time'), time);
+  if(u('u_mouse'))gl.uniform2f(u('u_mouse'), mx, my);
+  if(u('u_scene')){ gl.activeTexture(gl.TEXTURE0); gl.bindTexture(gl.TEXTURE_2D, tex); gl.uniform1i(u('u_scene'), 0); }
+  gl.drawArrays(gl.TRIANGLE_STRIP,0,4);
+}
+
+const T0 = performance.now();
+function frame(now){
+  const time = SHOT ? T : (now - T0)*0.001*speed;
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+  gl.viewport(0,0,cv.width,cv.height);
+  draw(PA, time);
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+  gl.viewport(0,0,cv.width,cv.height);
+  draw(PB, time);
+  osd.textContent = 'ice  ·  speed x' + speed + '  (- / =)  ·  move mouse';
+  if(SHOT) blit(); else requestAnimationFrame(frame);
+}
+
+function blit(){   // headless firefox won't composite a WebGL canvas, so hand pixels to a 2D canvas
+  const W=cv.width, H=cv.height, px=new Uint8Array(W*H*4);
+  gl.readPixels(0,0,W,H,gl.RGBA,gl.UNSIGNED_BYTE,px);
+  const out=document.createElement('canvas'); out.width=W; out.height=H; out.style.display='block';
+  const x=out.getContext('2d'), img=x.createImageData(W,H);
+  for(let y=0;y<H;y++) img.data.set(px.subarray((H-1-y)*W*4,(H-y)*W*4), y*W*4);
+  x.putImageData(img,0,0);
+  cv.remove(); document.body.appendChild(out);
+}
+
+if(PA && PB) SHOT ? frame(0) : requestAnimationFrame(frame);
+</script></body></html>
+"""
+
+out = (HTML.replace("__SCENE_B64__", __import__("base64").b64encode(scene.encode()).decode())
+           .replace("__ICE_B64__",   __import__("base64").b64encode(ice.encode()).decode()))
+open(os.path.join(here, out_f), "w").write(out)
+print(out_f, "written")
diff --git a/build_plasma.py b/build_plasma.py
new file mode 100644
index 0000000..5adbea0
--- /dev/null
+++ b/build_plasma.py
@@ -0,0 +1,123 @@
+#!/usr/bin/env python3
+"""Embed the two GLSL passes into the standalone ice_plasma.html page."""
+import json
+from pathlib import Path
+
+here = Path(__file__).resolve().parent
+scene = (here / '6_ice_plasma.frag').read_text()
+ice = (here / '7_ice_over.frag').read_text()
+html = r'''<!doctype html>
+<html lang="ru">
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width,initial-scale=1">
+<title>Сквозь лёд</title>
+<style>
+html,body{margin:0;width:100%;height:100%;overflow:hidden;background:#03111d}
+canvas{display:block;width:100%;height:100%;touch-action:none}
+#info{position:fixed;bottom:20px;left:24px;color:#d8f4ff;font:13px/1.6 system-ui,sans-serif;text-shadow:0 1px 5px #001;pointer-events:none}
+#info strong{font-weight:500} #info span{opacity:.75}
+</style>
+</head>
+<body>
+<canvas id="view" aria-label="Плазма под прозрачным льдом. Двигайте указатель для параллакса."></canvas>
+<div id="info" role="status"><strong>Сквозь лёд</strong><br><span id="help">Двигайте мышь · скорость − / =</span></div>
+<script>
+'use strict';
+const sceneSource = __SCENE__;
+const iceSource = __ICE__;
+const vertexSource = 'attribute vec2 p; void main(){gl_Position=vec4(p,0.0,1.0);}';
+const canvas = document.getElementById('view'), help = document.getElementById('help');
+const gl = canvas.getContext('webgl', {antialias:false, alpha:false, preserveDrawingBuffer:true});
+function fail(message) { help.textContent = message; throw new Error(message); }
+if (!gl) fail('WebGL недоступен в этом браузере.');
+function program(source) {
+  function shader(type, code) {
+    const s = gl.createShader(type);
+    gl.shaderSource(s, code); gl.compileShader(s);
+    if (!gl.getShaderParameter(s, gl.COMPILE_STATUS)) fail('Ошибка шейдера: ' + gl.getShaderInfoLog(s));
+    return s;
+  }
+  const p = gl.createProgram(), vs = shader(gl.VERTEX_SHADER, vertexSource), fs = shader(gl.FRAGMENT_SHADER, source);
+  gl.attachShader(p, vs); gl.attachShader(p, fs); gl.linkProgram(p);
+  gl.deleteShader(vs); gl.deleteShader(fs);
+  if (!gl.getProgramParameter(p, gl.LINK_STATUS)) fail('Ошибка программы: ' + gl.getProgramInfoLog(p));
+  return p;
+}
+const scene = program(sceneSource), ice = program(iceSource);
+const buffer = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
+gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1,-1,1,-1,-1,1,1,1]), gl.STATIC_DRAW);
+let texture, framebuffer, tileWidth, tileHeight;
+function resize() {
+  const max = gl.getParameter(gl.MAX_TEXTURE_SIZE);
+  const dpr = Math.min(devicePixelRatio || 1, 1.25, max / (innerWidth * 3), max / (innerHeight * 1.5));
+  canvas.width = Math.max(4, Math.floor(innerWidth * dpr / 4) * 4);
+  canvas.height = Math.max(4, Math.floor(innerHeight * dpr / 4) * 4);
+  tileWidth = canvas.width * 3 / 4; tileHeight = canvas.height * 3 / 4;
+  if (texture) gl.deleteTexture(texture);
+  if (framebuffer) gl.deleteFramebuffer(framebuffer);
+  texture = gl.createTexture(); gl.bindTexture(gl.TEXTURE_2D, texture);
+  gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, tileWidth * 4, tileHeight * 2, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+  framebuffer = gl.createFramebuffer(); gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
+  gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
+  if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) !== gl.FRAMEBUFFER_COMPLETE) fail('Не удалось создать текстуру сцены.');
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+}
+addEventListener('resize', resize); resize();
+const shot = location.hash.startsWith('#shot');
+const shotParams = new URLSearchParams(location.hash.slice(1));
+let mouseX = Number(shotParams.get('mx') ?? 0.5), mouseY = Number(shotParams.get('my') ?? 0.5);
+let speed = 1, time = Number(shotParams.get('t') ?? 0), previous;
+addEventListener('pointermove', e => { mouseX = e.clientX / innerWidth; mouseY = 1 - e.clientY / innerHeight; });
+addEventListener('keydown', e => {
+  if (e.key === '-' || e.key === '_') speed = Math.max(0.125, speed / 2);
+  else if (e.key === '=' || e.key === '+') speed = Math.min(4, speed * 2);
+  else return;
+  help.textContent = 'Двигайте мышь · скорость ' + speed + '×  (− / =)';
+});
+function draw(p, width, height) {
+  gl.useProgram(p);
+  const position = gl.getAttribLocation(p, 'p');
+  gl.bindBuffer(gl.ARRAY_BUFFER, buffer); gl.enableVertexAttribArray(position);
+  gl.vertexAttribPointer(position, 2, gl.FLOAT, false, 0, 0);
+  gl.uniform2f(gl.getUniformLocation(p, 'u_res'), width, height);
+  gl.uniform1f(gl.getUniformLocation(p, 'u_time'), time);
+  gl.uniform2f(gl.getUniformLocation(p, 'u_mouse'), mouseX, mouseY);
+  gl.uniform2f(gl.getUniformLocation(p, 'u_tile_res'), tileWidth, tileHeight);
+  gl.uniform1i(gl.getUniformLocation(p, 'u_scene'), 0);
+  gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
+}
+function frame(now) {
+  if (previous !== undefined) time += (now - previous) * 0.001 * speed;
+  previous = now;
+  gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
+  gl.viewport(0, 0, tileWidth * 4, tileHeight * 2);
+  draw(scene, tileWidth, tileHeight);
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+  gl.viewport(0, 0, canvas.width, canvas.height);
+  gl.activeTexture(gl.TEXTURE0); gl.bindTexture(gl.TEXTURE_2D, texture);
+  draw(ice, canvas.width, canvas.height);
+  if (shot) {
+    // Headless Firefox does not composite WebGL; expose the actual rendered pixels.
+    const pixels = new Uint8Array(canvas.width * canvas.height * 4);
+    gl.readPixels(0, 0, canvas.width, canvas.height, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
+    const output = document.createElement('canvas');
+    output.width = canvas.width; output.height = canvas.height;
+    const ctx = output.getContext('2d'), image = ctx.createImageData(output.width, output.height);
+    for (let y = 0; y < output.height; y++)
+      image.data.set(pixels.subarray((output.height - y - 1) * output.width * 4, (output.height - y) * output.width * 4), y * output.width * 4);
+    ctx.putImageData(image, 0, 0); canvas.replaceWith(output);
+  } else requestAnimationFrame(frame);
+}
+if (shot) frame(0); else requestAnimationFrame(frame);
+</script>
+</body>
+</html>
+'''
+(here / 'ice_plasma.html').write_text(html.replace('__SCENE__', json.dumps(scene)).replace('__ICE__', json.dumps(ice)))
+print('ice_plasma.html written')
diff --git a/ice.html b/ice.html
new file mode 100644
index 0000000..698a656
--- /dev/null
+++ b/ice.html
@@ -0,0 +1,92 @@
+<!doctype html><html><head><meta charset=utf-8><title>ice</title>
+<style>html,body{margin:0;height:100%;background:#000;overflow:hidden}
+canvas{display:block;width:100vw;height:100vh}
+#osd{position:fixed;left:14px;bottom:12px;font:13px ui-monospace,monospace;color:#9cf;opacity:.7;pointer-events:none}</style>
+</head><body><canvas id=c></canvas><div id=osd></div><script>
+const FRAG_A = atob('Ly8gUGFzcyBBOiBpY3kgc2NlbmUuIFJHQiA9IGNvbG91ciwgQSA9IGxpbmVhciBkZXB0aCAvIDguMCAgKG91ciB6LWJ1ZmZlcikKcHJlY2lzaW9uIGhpZ2hwIGZsb2F0Owp1bmlmb3JtIHZlYzIgdV9yZXM7IHVuaWZvcm0gZmxvYXQgdV90aW1lOyB1bmlmb3JtIHZlYzIgdV9tb3VzZTsKCmZsb2F0IHNkU3BoZXJlKHZlYzMgcCwgZmxvYXQgcil7IHJldHVybiBsZW5ndGgocCkgLSByOyB9CgpmbG9hdCBtYXAodmVjMyBwKXsKICBmbG9hdCBkID0gc2RTcGhlcmUocCwgMS4wKTsKICBmb3IoaW50IGk9MDtpPDM7aSsrKXsKICAgIGZsb2F0IGZpID0gZmxvYXQoaSk7CiAgICB2ZWMzIHEgPSBwOwogICAgZmxvYXQgYSA9IHVfdGltZSowLjUgKyBmaSoyLjE7CiAgICBxLnh6ID0gbWF0Mihjb3MoYSksLXNpbihhKSxzaW4oYSksY29zKGEpKSAqIHEueHo7CiAgICBkID0gbWluKGQsIHNkU3BoZXJlKHEgLSB2ZWMzKDAuNzUsMC4wLDAuMCksIDAuMzQpKTsKICB9CiAgcmV0dXJuIGQ7Cn0KCnZvaWQgbWFpbigpewogIHZlYzIgdXYgPSAoZ2xfRnJhZ0Nvb3JkLnh5IC0gMC41KnVfcmVzKS91X3Jlcy55OwogIHZlYzMgcm8gPSB2ZWMzKDAuMCwwLjAsOC41KTsKICB2ZWMzIHJkID0gbm9ybWFsaXplKHZlYzModXYsIC0xLjYpKTsKCiAgZmxvYXQgdCA9IDAuMDsgaW50IGhpdCA9IDA7CiAgZm9yKGludCBpPTA7aTw5MDtpKyspewogICAgZmxvYXQgZCA9IG1hcChybyArIHJkKnQpOwogICAgaWYoZCA8IDAuMDAxKXsgaGl0ID0gMTsgYnJlYWs7IH0KICAgIHQgKz0gZDsKICAgIGlmKHQgPiAxMi4wKSBicmVhazsKICB9CgogIHZlYzMgY29sID0gdmVjMygwLjAwOCwwLjAyLDAuMDQ1KTsKICBjb2wgKz0gMC4wNypwb3coMS4wIC0gYWJzKHV2LnkpKjAuOSwgNC4wKSp2ZWMzKDAuMTUsMC4zNSwwLjYpOyAgIC8vIGNvbGQgaGF6ZQogIGZsb2F0IGRlcHRoID0gMTIuMDsKCiAgaWYoaGl0ID09IDEpewogICAgZGVwdGggPSB0OwogICAgdmVjMyBwb3MgPSBybyArIHJkKnQ7CiAgICB2ZWMzIG4gPSBub3JtYWxpemUodmVjMyhtYXAocG9zK3ZlYzMoMC4wMDEsMCwwKSktbWFwKHBvcy12ZWMzKDAuMDAxLDAsMCkpLAogICAgICAgICAgICAgICAgICAgICAgICAgICAgbWFwKHBvcyt2ZWMzKDAsMC4wMDEsMCkpLW1hcChwb3MtdmVjMygwLDAuMDAxLDApKSwKICAgICAgICAgICAgICAgICAgICAgICAgICAgIG1hcChwb3MrdmVjMygwLDAsMC4wMDEpKS1tYXAocG9zLXZlYzMoMCwwLDAuMDAxKSkpKTsKICAgIHZlYzMgbCA9IG5vcm1hbGl6ZSh2ZWMzKDAuNDUsMC44NSwwLjU1KSk7CiAgICBmbG9hdCBkaWYgPSBtYXgoZG90KG4sbCksMC4wKTsKICAgIGZsb2F0IGZyZSA9IHBvdygxLjAgLSBtYXgoZG90KG4sLXJkKSwwLjApLCAzLjApOwoKICAgIC8vIGZyb3plbiBsYXllcnMgaW5zdGVhZCBvZiByYWluYm93CiAgICBmbG9hdCBmID0gMC41ICsgMC41KnNpbihwb3MueSoyMC4wICsgdV90aW1lKjIuMCArIHBvcy54KjUuMCArIG4ueiozLjApOwogICAgdmVjMyBhbGIgPSBtaXgodmVjMygwLjkwLDAuOTcsMS4wMCksIHZlYzMoMC4zNCwwLjY2LDAuOTIpLCBmKTsKICAgIGNvbCA9IGFsYiooMC4wNiArIDEuMDUqZGlmKSArIHZlYzMoMC42MCwwLjkwLDEuMCkqZnJlKjEuNjsKICAgIGNvbCAqPSAwLjg2ICsgMC4xNCpzaW4ocG9zLnkqMzguMCArIHVfdGltZSo0LjApOwogIH0KCiAgLy8gZGVwdGggZm9nOiBmYXIgdGhpbmdzIGZhZGUgaW50byB0aGUgY29sZCB2b2lkCiAgY29sID0gbWl4KGNvbCwgdmVjMygwLjAzLDAuMTAsMC4xOSksIHNtb290aHN0ZXAoMy4wLCAxMi4wLCBkZXB0aCkqMC44NSk7CiAgZ2xfRnJhZ0NvbG9yID0gdmVjNChjb2wsIGNsYW1wKGRlcHRoLzEyLjAsIDAuMCwgMS4wKSk7Cn0K');
+const FRAG_B = atob('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');
+const VS = 'attribute vec2 p;void main(){gl_Position=vec4(p,0,1);}';
+const SHOT = location.hash.indexOf('shot') >= 0;
+const T = parseFloat((location.hash.match(/t=([\d.]+)/)||[0,0])[1]) || 0;
+const cv = document.getElementById('c'), osd = document.getElementById('osd');
+const gl = cv.getContext('webgl', {antialias:false, preserveDrawingBuffer:SHOT});
+
+function prog(vs, fs){
+  const sh=(t,s)=>{const o=gl.createShader(t);gl.shaderSource(o,s);gl.compileShader(o);
+    if(!gl.getShaderParameter(o,gl.COMPILE_STATUS)) throw new Error(gl.getShaderInfoLog(o)); return o;};
+  const p=gl.createProgram();
+  gl.attachShader(p,sh(gl.VERTEX_SHADER,vs)); gl.attachShader(p,sh(gl.FRAGMENT_SHADER,fs));
+  gl.linkProgram(p); if(!gl.getProgramParameter(p,gl.LINK_STATUS)) throw new Error(gl.getProgramInfoLog(p));
+  return p;
+}
+let PA, PB;
+try { PA = prog(VS, FRAG_A); PB = prog(VS, FRAG_B); }
+catch(e){ osd.textContent = 'shader error: ' + e.message; document.title = 'ERR'; }
+
+const buf = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1,-1,1,-1,-1,1,1,1]), gl.STATIC_DRAW);
+
+// offscreen target: colour + depth packed into alpha
+let fbo, tex;
+function resize(){
+  const d = SHOT ? 1 : (devicePixelRatio||1);
+  const W = SHOT ? parseInt(location.hash.match(/w=(\d+)/)?.[1]||700) : Math.round(innerWidth*d);
+  const H = SHOT ? W : Math.round(innerHeight*d);
+  cv.width=W; cv.height=H; cv.style.width = SHOT ? W+'px' : '100vw'; cv.style.height = SHOT ? H+'px' : '100vh';
+  tex = gl.createTexture();
+  gl.bindTexture(gl.TEXTURE_2D, tex);
+  gl.texImage2D(gl.TEXTURE_2D,0,gl.RGBA,W,H,0,gl.RGBA,gl.UNSIGNED_BYTE,null);
+  gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_MIN_FILTER,gl.LINEAR);
+  gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_MAG_FILTER,gl.LINEAR);
+  gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_WRAP_S,gl.CLAMP_TO_EDGE);
+  gl.texParameteri(gl.TEXTURE_2D,gl.TEXTURE_WRAP_T,gl.CLAMP_TO_EDGE);
+  fbo = gl.createFramebuffer();
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+  gl.framebufferTexture2D(gl.FRAMEBUFFER,gl.COLOR_ATTACHMENT0,gl.TEXTURE_2D,tex,0);
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+}
+resize();
+
+let mx=0.5, my=0.5;
+if(!SHOT){
+  addEventListener('resize', resize);
+  addEventListener('mousemove', e=>{ mx=e.clientX/innerWidth; my=1-e.clientY/innerHeight; });
+}
+
+function draw(p, time){
+  gl.useProgram(p);
+  const l = gl.getAttribLocation(p,'p');
+  gl.bindBuffer(gl.ARRAY_BUFFER, buf);
+  gl.enableVertexAttribArray(l); gl.vertexAttribPointer(l,2,gl.FLOAT,false,0,0);
+  const u = n => gl.getUniformLocation(p,n);
+  if(u('u_res'))  gl.uniform2f(u('u_res'), cv.width, cv.height);
+  if(u('u_time')) gl.uniform1f(u('u_time'), time);
+  if(u('u_mouse'))gl.uniform2f(u('u_mouse'), mx, my);
+  if(u('u_scene')){ gl.activeTexture(gl.TEXTURE0); gl.bindTexture(gl.TEXTURE_2D, tex); gl.uniform1i(u('u_scene'), 0); }
+  gl.drawArrays(gl.TRIANGLE_STRIP,0,4);
+}
+
+function frame(time){
+  gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
+  gl.viewport(0,0,cv.width,cv.height);
+  draw(PA, time);
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+  gl.viewport(0,0,cv.width,cv.height);
+  draw(PB, time);
+  osd.textContent = 'ice  ·  move mouse  ·  ' + cv.width + 'x' + cv.height;
+  if(SHOT) blit(); else requestAnimationFrame(frame);
+}
+
+function blit(){   // headless firefox won't composite a WebGL canvas, so hand pixels to a 2D canvas
+  const W=cv.width, H=cv.height, px=new Uint8Array(W*H*4);
+  gl.readPixels(0,0,W,H,gl.RGBA,gl.UNSIGNED_BYTE,px);
+  const out=document.createElement('canvas'); out.width=W; out.height=H; out.style.display='block';
+  const x=out.getContext('2d'), img=x.createImageData(W,H);
+  for(let y=0;y<H;y++) img.data.set(px.subarray((H-1-y)*W*4,(H-y)*W*4), y*W*4);
+  x.putImageData(img,0,0);
+  cv.remove(); document.body.appendChild(out);
+}
+
+if(PA && PB) frame(SHOT ? T : 0);
+</script></body></html>
diff --git a/ice_plasma.gif b/ice_plasma.gif
new file mode 100644
index 0000000..f0afb70
Binary files /dev/null and b/ice_plasma.gif differ
diff --git a/ice_plasma.html b/ice_plasma.html
new file mode 100644
index 0000000..46ebe73
--- /dev/null
+++ b/ice_plasma.html
@@ -0,0 +1,112 @@
+<!doctype html>
+<html lang="ru">
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width,initial-scale=1">
+<title>Сквозь лёд</title>
+<style>
+html,body{margin:0;width:100%;height:100%;overflow:hidden;background:#03111d}
+canvas{display:block;width:100%;height:100%;touch-action:none}
+#info{position:fixed;bottom:20px;left:24px;color:#d8f4ff;font:13px/1.6 system-ui,sans-serif;text-shadow:0 1px 5px #001;pointer-events:none}
+#info strong{font-weight:500} #info span{opacity:.75}
+</style>
+</head>
+<body>
+<canvas id="view" aria-label="Плазма под прозрачным льдом. Двигайте указатель для параллакса."></canvas>
+<div id="info" role="status"><strong>Сквозь лёд</strong><br><span id="help">Двигайте мышь · скорость − / =</span></div>
+<script>
+'use strict';
+const sceneSource = "// Pass 1: eight plasma sheets, one atlas tile each. Alpha stores linear depth.\n// Density field lit as a height surface: billowing volumes with a real terminator.\nprecision highp float;\nuniform vec2 u_res; // size of one tile\nuniform float u_time;\n\nfloat hash(vec2 p) { return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453); }\nfloat noise(vec2 p) {\n  vec2 i = floor(p), f = fract(p);\n  f = f*f*(3.0-2.0*f);\n  return mix(mix(hash(i), hash(i+vec2(1.0,0.0)), f.x),\n             mix(hash(i+vec2(0.0,1.0)), hash(i+vec2(1.0,1.0)), f.x), f.y);\n}\nfloat fbm(vec2 p) {\n  float sum = 0.0, amp = 0.5;\n  for (int i = 0; i < 4; i++) {\n    sum += amp * noise(p);\n    p = mat2(1.62, 1.17, -1.17, 1.62) * p;\n    amp *= 0.5;\n  }\n  return sum;\n}\nfloat fbm2(vec2 p) {\n  return 0.5 * noise(p) + 0.25 * noise(mat2(1.62, 1.17, -1.17, 1.62) * p);\n}\nconst float EXTENT = 3.8; // half-width of a sheet in world units; must match the ice pass\n\nvoid main() {\n  vec2 tile = floor(gl_FragCoord.xy / u_res);\n  float layer = tile.x + tile.y * 4.0;\n  vec2 uv = fract(gl_FragCoord.xy / u_res);\n  vec2 p = (uv - 0.5) * 2.0 * vec2(EXTENT * u_res.x / u_res.y, EXTENT);\n  p *= 0.85 + 0.10 * layer; // far sheets carry finer detail, which reads as distance\n  float angle = hash(vec2(layer, 3.1)) * 6.2831853;\n  p = mat2(cos(angle), sin(angle), -sin(angle), cos(angle)) * p;\n\n  // Periodic time: every field returns exactly after 30 seconds.\n  float phase = u_time * 6.2831853 / 30.0;\n  vec2 o = vec2(cos(phase), sin(phase));\n  vec2 seed = vec2(layer * 17.3, layer * 9.1);\n\n  // Two nested warp stages, the marbled-plasma motion.\n  vec2 q = vec2(fbm(p * 0.50 + seed + o * 0.55),\n                fbm(p * 0.50 + seed + 23.1 - o * 0.55));\n  vec2 r = vec2(fbm(p * 0.85 + 2.0 * q + seed + vec2(o.y, -o.x) * 0.40),\n                fbm(p * 0.85 + 2.0 * q + seed + 31.7 - vec2(o.y, -o.x) * 0.40));\n  vec2 w = p * 1.10 + 2.6 * r + seed;   // warped coords of the density field\n\n  // The silhouette is shared by all sheets (slid a little per depth), so the gaps\n  // stay open right through the stack instead of filling in with overlap.\n  float mass = smoothstep(0.520, 0.548, fbm((p + o * 0.30 + vec2(0.10, -0.07) * layer) * 0.62 + r * 1.1 + 13.7));\n\n  // Light the density as a height surface: $cheap 2-octave gradient, strong terminator.\n  float h = 0.05;\n  vec2 slope = vec2(fbm2(w + vec2(h, 0.0)) - fbm2(w - vec2(h, 0.0)),\n                    fbm2(w + vec2(0.0, h)) - fbm2(w - vec2(0.0, h))) * (10.0 / (2.0 * h));\n  vec3 nrm = normalize(vec3(-slope, 1.0));\n  float lit = clamp(dot(nrm, normalize(vec3(-0.38, 0.52, 0.76))), 0.0, 1.0);\n\n  // Folded planes across the volume, feathered so they never read as a grid.\n  vec2 g = (p + r * 2.0) * 1.4;\n  vec2 cell = floor(g), f = fract(g);\n  float feather = smoothstep(0.0, 0.10, min(min(f.x, 1.0 - f.x), min(f.y, 1.0 - f.y)));\n  float facet = mix(1.0, mix(0.70, 1.25, hash(cell + seed + step(1.0, f.x + f.y) * 37.0)), feather);\n\n  float shade = 0.60 + 0.55 * lit;                      // soft light across the folded planes\n  float e = mass * facet * shade * 0.075\n          + mass * (1.0 - mass) * 4.0 * 0.015           // thin torn silhouette\n          + mass * pow(lit, 14.0) * 0.045;              // glint where a fold faces the light\n  vec3 col = e * mix(vec3(0.02, 0.42, 0.60), vec3(0.08, 0.64, 0.88), facet * 0.5);\n  // Faint dye in the open gaps so darkness reads as depth, not as a hole.\n  col += smoothstep(0.40, 0.85, fbm(p * 0.30 + seed * 0.4 + o * 0.3)) * vec3(0.0001, 0.0004, 0.0006);\n\n  gl_FragColor = vec4(col, (0.42 + layer * 0.26) / 2.6);\n}\n";
+const iceSource = "// Pass 2: clean ice. Refraction, chromatic shear, absorption by true path length.\n// Nothing is added to empty space, so the gaps between sheets stay black.\nprecision highp float;\nuniform vec2 u_res;\nuniform float u_time;\nuniform vec2 u_mouse; // normalized, bottom-left origin\nuniform sampler2D u_scene;\nuniform vec2 u_tile_res;\n\nconst float EXTENT = 3.8;                 // must match the plasma pass\nconst float FRONT  = -2.0;                // ice surface, camera at the origin looking down -z\nconst vec3  SIGMA  = vec3(0.66, 0.26, 0.11); // absorption per unit: red dies first, so depth turns blue\nconst float IOR    = 1.31;\n\nfloat hash(vec2 p) { return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453); }\nfloat noise(vec2 p) {\n  vec2 i = floor(p), f = fract(p);\n  f = f*f*(3.0-2.0*f);\n  return mix(mix(hash(i), hash(i+vec2(1.0,0.0)), f.x),\n             mix(hash(i+vec2(0.0,1.0)), hash(i+vec2(1.0,1.0)), f.x), f.y);\n}\nfloat fbm(vec2 p) {\n  float sum = 0.0, amp = 0.5;\n  for (int i = 0; i < 3; i++) { sum += amp * noise(p); p = mat2(1.62, 1.17, -1.17, 1.62) * p; amp *= 0.5; }\n  return sum;\n}\nvec2 atlasUV(vec2 world, float layer) {\n  vec2 uv = world / (2.0 * EXTENT) + 0.5;\n  uv = clamp(uv, 0.5 / u_tile_res, 1.0 - 0.5 / u_tile_res); // keep bilinear taps inside the tile\n  return (vec2(mod(layer, 4.0), floor(layer / 4.0)) + uv) / vec2(4.0, 2.0);\n}\n// Smooth frozen surface: two octaves, no bubbles, no grain.\nfloat height(vec2 x) {\n  return 0.22 * fbm(x * 0.85 + 2.0) + 0.06 * fbm(x * 2.6 - 5.0);\n}\nvoid main() {\n  vec2 screen = gl_FragCoord.xy / u_res;\n  vec2 p = (gl_FragCoord.xy - 0.5 * u_res) / u_res.y;\n  vec2 look = clamp(u_mouse - 0.5, -0.35, 0.35); // orbiting the slab centre\n  vec3 ray = normalize(vec3(p - look * 2.2, -1.6));\n\n  // Front surface along the view ray; two fixed-point steps settle on the swell.\n  float t = FRONT / ray.z;\n  for (int i = 0; i < 2; i++) t = (FRONT + height(ray.xy * t)) / ray.z;\n  vec3 hit = ray * t;\n\n  float e = 0.02;\n  vec2 slope = vec2(height(hit.xy + vec2(e, 0.0)) - height(hit.xy - vec2(e, 0.0)),\n                    height(hit.xy + vec2(0.0, e)) - height(hit.xy - vec2(0.0, e))) / (2.0 * e);\n  float bevel = smoothstep(0.14, 0.0, min(min(screen.x, 1.0 - screen.x), min(screen.y, 1.0 - screen.y)));\n  slope += bevel * (screen - 0.5) * 0.55; // the slab turns away at the frame edge\n  vec3 normal = normalize(vec3(-slope, 1.0));\n  float facing = max(dot(-ray, normal), 0.0);\n\n  // Refracted ray; red and blue bend a little differently, which is what makes ice ring.\n  vec3 inside = refract(ray, normal, 1.0 / IOR);\n  vec2 shearR = (refract(ray, normal, 1.0 / (IOR - 0.012)) - inside).xy;\n  vec2 shearB = (refract(ray, normal, 1.0 / (IOR + 0.016)) - inside).xy;\n  inside = normalize(inside);\n  if (inside.z > -0.05) inside = vec3(0.0, 0.0, -1.0);\n\n  // Recentre the parallax on the middle of the sheet stack: near and far sheets\n  // then slide past each other at different rates as the pointer moves.\n  vec2 par = look * 4.54;\n\n  vec3 acc = vec3(0.0);\n  float trans = 1.0;\n  for (int i = 0; i < 8; i++) {\n    float layer = float(i);\n    float depth = texture2D(u_scene, atlasUV(hit.xy + par, layer)).a * 2.6; // depth buffer from pass 1\n    float path = (hit.z - (FRONT - depth)) / -inside.z;                     // ice crossed to reach this sheet\n    vec2 at = (hit + inside * path).xy + par;\n    vec3 plasma;\n    plasma.r = texture2D(u_scene, atlasUV(at + shearR * path, layer)).r;\n    plasma.g = texture2D(u_scene, atlasUV(at, layer)).g;\n    plasma.b = texture2D(u_scene, atlasUV(at + shearB * path, layer)).b;\n    vec3 c = plasma * exp(-SIGMA * path);\n    // Near plumes are nearly opaque, so the sheets behind them show through the gaps\n    // instead of averaging into a wash. That is what makes the stack read as depth.\n    float alpha = clamp(max(max(c.r, c.g), c.b) * 1.8, 0.0, 0.80);\n    acc += trans * c;\n    trans *= 1.0 - alpha;\n  }\n\n  // Gentle shoulder: overlapping glow stays coloured instead of clipping to white.\n  vec3 col = vec3(1.0) - exp(-acc * 1.5);\n\n  // Glass: reflection and a rim only where the surface turns away. Empty space stays dark.\n  float fresnel = pow(1.0 - facing, 5.0);\n  vec3 sky = mix(vec3(0.004, 0.016, 0.030), vec3(0.075, 0.220, 0.320), normal.y * 0.5 + 0.5);\n  col += sky * (fresnel * 1.2 + bevel * 0.03);\n\n  gl_FragColor = vec4(pow(clamp(col, 0.0, 1.0), vec3(0.4545)), 1.0);\n}\n";
+const vertexSource = 'attribute vec2 p; void main(){gl_Position=vec4(p,0.0,1.0);}';
+const canvas = document.getElementById('view'), help = document.getElementById('help');
+const gl = canvas.getContext('webgl', {antialias:false, alpha:false, preserveDrawingBuffer:true});
+function fail(message) { help.textContent = message; throw new Error(message); }
+if (!gl) fail('WebGL недоступен в этом браузере.');
+function program(source) {
+  function shader(type, code) {
+    const s = gl.createShader(type);
+    gl.shaderSource(s, code); gl.compileShader(s);
+    if (!gl.getShaderParameter(s, gl.COMPILE_STATUS)) fail('Ошибка шейдера: ' + gl.getShaderInfoLog(s));
+    return s;
+  }
+  const p = gl.createProgram(), vs = shader(gl.VERTEX_SHADER, vertexSource), fs = shader(gl.FRAGMENT_SHADER, source);
+  gl.attachShader(p, vs); gl.attachShader(p, fs); gl.linkProgram(p);
+  gl.deleteShader(vs); gl.deleteShader(fs);
+  if (!gl.getProgramParameter(p, gl.LINK_STATUS)) fail('Ошибка программы: ' + gl.getProgramInfoLog(p));
+  return p;
+}
+const scene = program(sceneSource), ice = program(iceSource);
+const buffer = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
+gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1,-1,1,-1,-1,1,1,1]), gl.STATIC_DRAW);
+let texture, framebuffer, tileWidth, tileHeight;
+function resize() {
+  const max = gl.getParameter(gl.MAX_TEXTURE_SIZE);
+  const dpr = Math.min(devicePixelRatio || 1, 1.25, max / (innerWidth * 3), max / (innerHeight * 1.5));
+  canvas.width = Math.max(4, Math.floor(innerWidth * dpr / 4) * 4);
+  canvas.height = Math.max(4, Math.floor(innerHeight * dpr / 4) * 4);
+  tileWidth = canvas.width * 3 / 4; tileHeight = canvas.height * 3 / 4;
+  if (texture) gl.deleteTexture(texture);
+  if (framebuffer) gl.deleteFramebuffer(framebuffer);
+  texture = gl.createTexture(); gl.bindTexture(gl.TEXTURE_2D, texture);
+  gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, tileWidth * 4, tileHeight * 2, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+  framebuffer = gl.createFramebuffer(); gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
+  gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
+  if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) !== gl.FRAMEBUFFER_COMPLETE) fail('Не удалось создать текстуру сцены.');
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+}
+addEventListener('resize', resize); resize();
+const shot = location.hash.startsWith('#shot');
+const shotParams = new URLSearchParams(location.hash.slice(1));
+let mouseX = Number(shotParams.get('mx') ?? 0.5), mouseY = Number(shotParams.get('my') ?? 0.5);
+let speed = 1, time = Number(shotParams.get('t') ?? 0), previous;
+addEventListener('pointermove', e => { mouseX = e.clientX / innerWidth; mouseY = 1 - e.clientY / innerHeight; });
+addEventListener('keydown', e => {
+  if (e.key === '-' || e.key === '_') speed = Math.max(0.125, speed / 2);
+  else if (e.key === '=' || e.key === '+') speed = Math.min(4, speed * 2);
+  else return;
+  help.textContent = 'Двигайте мышь · скорость ' + speed + '×  (− / =)';
+});
+function draw(p, width, height) {
+  gl.useProgram(p);
+  const position = gl.getAttribLocation(p, 'p');
+  gl.bindBuffer(gl.ARRAY_BUFFER, buffer); gl.enableVertexAttribArray(position);
+  gl.vertexAttribPointer(position, 2, gl.FLOAT, false, 0, 0);
+  gl.uniform2f(gl.getUniformLocation(p, 'u_res'), width, height);
+  gl.uniform1f(gl.getUniformLocation(p, 'u_time'), time);
+  gl.uniform2f(gl.getUniformLocation(p, 'u_mouse'), mouseX, mouseY);
+  gl.uniform2f(gl.getUniformLocation(p, 'u_tile_res'), tileWidth, tileHeight);
+  gl.uniform1i(gl.getUniformLocation(p, 'u_scene'), 0);
+  gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
+}
+function frame(now) {
+  if (previous !== undefined) time += (now - previous) * 0.001 * speed;
+  previous = now;
+  gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
+  gl.viewport(0, 0, tileWidth * 4, tileHeight * 2);
+  draw(scene, tileWidth, tileHeight);
+  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+  gl.viewport(0, 0, canvas.width, canvas.height);
+  gl.activeTexture(gl.TEXTURE0); gl.bindTexture(gl.TEXTURE_2D, texture);
+  draw(ice, canvas.width, canvas.height);
+  if (shot) {
+    // Headless Firefox does not composite WebGL; expose the actual rendered pixels.
+    const pixels = new Uint8Array(canvas.width * canvas.height * 4);
+    gl.readPixels(0, 0, canvas.width, canvas.height, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
+    const output = document.createElement('canvas');
+    output.width = canvas.width; output.height = canvas.height;
+    const ctx = output.getContext('2d'), image = ctx.createImageData(output.width, output.height);
+    for (let y = 0; y < output.height; y++)
+      image.data.set(pixels.subarray((output.height - y - 1) * output.width * 4, (output.height - y) * output.width * 4), y * output.width * 4);
+    ctx.putImageData(image, 0, 0); canvas.replaceWith(output);
+  } else requestAnimationFrame(frame);
+}
+if (shot) frame(0); else requestAnimationFrame(frame);
+</script>
+</body>
+</html>
diff --git a/playground.html b/playground.html
new file mode 100644
index 0000000..d6bcc08
--- /dev/null
+++ b/playground.html
@@ -0,0 +1,36 @@
+<!doctype html><html><head><meta charset=utf-8><title>shaders</title>
+<style>html,body{margin:0;height:100%;background:#000;overflow:hidden}
+canvas{display:block;width:100vw;height:100vh}
+#osd{position:fixed;left:14px;bottom:12px;font:13px ui-monospace,monospace;color:#9bf;opacity:.75;pointer-events:none}</style>
+</head><body><canvas id=c></canvas><div id=osd></div><script>
+const SHADERS = ["precision highp float;\nuniform vec2 u_res; uniform float u_time; uniform vec2 u_mouse;\nfloat hash(vec2 p){return fract(sin(dot(p,vec2(127.1,311.7)))*43758.5453);}\nfloat noise(vec2 p){vec2 i=floor(p),f=fract(p);f=f*f*(3.0-2.0*f);\n return mix(mix(hash(i),hash(i+vec2(1,0)),f.x),mix(hash(i+vec2(0,1)),hash(i+vec2(1,1)),f.x),f.y);}\nfloat fbm(vec2 p){float a=0.5,s=0.0;for(int i=0;i<5;i++){s+=a*noise(p);p*=2.03;a*=0.5;}return s;}\nvoid main(){\n vec2 p=(gl_FragCoord.xy-0.5*u_res)/u_res.y;\n float t=u_time*0.15;\n vec2 q=vec2(fbm(p*2.0+vec2(0.0,t)),fbm(p*2.0+vec2(5.2,-t)));\n vec2 r=vec2(fbm(p*2.0+q*1.8+vec2(1.7,9.2)+t*1.3),fbm(p*2.0+q*1.8+vec2(8.3,2.8)-t*1.1));\n float v=fbm(p*2.0+r*2.2);\n vec3 col=mix(vec3(0.02,0.03,0.10),vec3(0.85,0.25,0.35),smoothstep(0.2,0.9,v));\n col=mix(col,vec3(0.15,0.65,0.95),smoothstep(0.5,1.0,length(r-0.5)));\n col+=0.35*pow(max(0.0,1.0-length(p*0.9)),3.0)*vec3(1.0,0.85,0.6);\n col*=1.0-0.5*length(p)*0.4;\n gl_FragColor=vec4(col,1.0);\n}\n", "precision highp float;\nuniform vec2 u_res; uniform float u_time; uniform vec2 u_mouse;\nvoid main(){\n vec2 p=(gl_FragCoord.xy-0.5*u_res)/u_res.y;\n float t=u_time*0.6;\n float a=atan(p.y,p.x);\n float r=length(p)+0.001;\n float z=1.0/r+t;\n float rings=fract(z*2.0+a*0.6+sin(a*3.0+t)*0.3);\n vec3 base=mix(vec3(1.0,0.15,0.55),vec3(0.15,0.9,1.0),smoothstep(0.0,1.0,rings));\n float glow=pow(1.0-r,2.0);\n float band=smoothstep(0.45,0.5,rings)*smoothstep(0.6,0.5,rings);\n vec3 col=base*band*glow*2.2;\n col+=vec3(0.9,0.5,1.0)*pow(glow,8.0)*1.5;\n col+=0.02*vec3(0.3,0.1,0.5)/(r*r);\n gl_FragColor=vec4(col,1.0);\n}\n", "precision highp float;\nuniform vec2 u_res; uniform float u_time; uniform vec2 u_mouse;\nfloat sdSphere(vec3 p,float r){return length(p)-r;}\nfloat map(vec3 p){\n float d=sdSphere(p,1.0);\n for(int i=0;i<3;i++){\n  float fi=float(i);\n  vec3 q=p; float a=u_time*0.5+fi*2.1;\n  q.xz=mat2(cos(a),-sin(a),sin(a),cos(a))*q.xz;\n  d=min(d,sdSphere(q-vec3(0.75,0.0,0.0),0.34));\n }\n return d;\n}\nvoid main(){\n vec2 uv=(gl_FragCoord.xy-0.5*u_res)/u_res.y;\n vec3 ro=vec3(0.0,0.0,3.6), rd=normalize(vec3(uv,-1.6));\n float tt=0.0; int hit=0;\n for(int i=0;i<80;i++){\n  float d=map(ro+rd*tt);\n  if(d<0.001){hit=1;break;}\n  tt+=d;\n  if(tt>8.0)break;\n }\n vec3 col=vec3(0.03,0.04,0.07)+0.15*pow(1.0-abs(uv.y),3.0);\n if(hit==1){\n  vec3 pos=ro+rd*tt;\n  vec3 n=normalize(vec3(map(pos+vec3(0.001,0,0))-map(pos-vec3(0.001,0,0)),\n                        map(pos+vec3(0,0.001,0))-map(pos-vec3(0,0.001,0)),\n                        map(pos+vec3(0,0,0.001))-map(pos-vec3(0,0,0.001))));\n  vec3 l=normalize(vec3(0.6,0.8,0.5));\n  float dif=max(dot(n,l),0.0);\n  float fre=pow(1.0-max(dot(n,-rd),0.0),3.0);\n  vec3 alb=0.5+0.5*cos(6.2831*(pos*0.6+vec3(0.0,0.33,0.67)));\n  col=alb*(0.15+0.85*dif)+vec3(0.6,0.8,1.0)*fre*1.2;\n  col*=0.9+0.1*sin(pos.y*40.0+u_time*4.0);\n }\n gl_FragColor=vec4(pow(col,vec3(0.4545)),1.0);\n}\n"];
+const NAMES = ["1_plasma", "2_tunnel", "3_orb"];
+const VS='attribute vec2 p;void main(){gl_Position=vec4(p,0,1);}';
+const c=document.getElementById('c'),osd=document.getElementById('osd');
+const gl=c.getContext('webgl',{antialias:false,preserveDrawingBuffer:false});
+let progs=[],cur=0,mx=0.5,my=0.5,t0=performance.now();
+function sh(t,s){const o=gl.createShader(t);gl.shaderSource(o,s);gl.compileShader(o);
+ if(!gl.getShaderParameter(o,gl.COMPILE_STATUS)){osd.textContent='compile error: '+gl.getShaderInfoLog(o);console.error(gl.getShaderInfoLog(o));}
+ return o;}
+for(const s of SHADERS){const pr=gl.createProgram();
+ gl.attachShader(pr,sh(gl.VERTEX_SHADER,VS));gl.attachShader(pr,sh(gl.FRAGMENT_SHADER,s));
+ gl.linkProgram(pr);progs.push(pr);}
+const b=gl.createBuffer();gl.bindBuffer(gl.ARRAY_BUFFER,b);
+gl.bufferData(gl.ARRAY_BUFFER,new Float32Array([-1,-1,1,-1,-1,1,1,1]),gl.STATIC_DRAW);
+function resize(){const d=devicePixelRatio||1;c.width=innerWidth*d;c.height=innerHeight*d;}
+addEventListener('resize',resize);resize();
+addEventListener('mousemove',e=>{mx=e.clientX/innerWidth;my=1-e.clientY/innerHeight;});
+addEventListener('keydown',e=>{if(e.key>='1'&&e.key<=String(progs.length)){cur=+e.key-1;}});
+function frame(){
+ const pr=progs[cur];gl.useProgram(pr);
+ const l=gl.getAttribLocation(pr,'p');gl.enableVertexAttribArray(l);
+ gl.vertexAttribPointer(l,2,gl.FLOAT,false,0,0);
+ gl.uniform2f(gl.getUniformLocation(pr,'u_res'),c.width,c.height);
+ gl.uniform1f(gl.getUniformLocation(pr,'u_time'),(performance.now()-t0)/1000);
+ gl.uniform2f(gl.getUniformLocation(pr,'u_mouse'),mx,my);
+ gl.viewport(0,0,c.width,c.height);gl.drawArrays(gl.TRIANGLE_STRIP,0,4);
+ osd.textContent=NAMES[cur]+'  ['+(cur+1)+'/'+progs.length+']  ·  keys 1-'+progs.length+' switch · move mouse';
+ requestAnimationFrame(frame);
+}
+frame();
+</script></body></html>
diff --git a/preview.png b/preview.png
new file mode 100644
index 0000000..f1b37b3
Binary files /dev/null and b/preview.png differ
diff --git a/preview_ice.png b/preview_ice.png
new file mode 100644
index 0000000..d81d36f
Binary files /dev/null and b/preview_ice.png differ
diff --git a/render.py b/render.py
new file mode 100755
index 0000000..efdd2bc
--- /dev/null
+++ b/render.py
@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+"""Render a GLSL fragment shader to PNG via headless firefox (readPixels -> 2D canvas).
+
+usage: ./render.py shader.frag out.png [time] [width] [height] [mouseX] [mouseY]
+"""
+import base64, os, subprocess, sys, tempfile
+
+HTML = """<!doctype html><html><body style="margin:0;background:#000">
+<canvas id=c width=%(w)d height=%(h)d></canvas><script>
+const W=%(w)d,H=%(h)d,FRAG=%(frag)s,VS='attribute vec2 p;void main(){gl_Position=vec4(p,0,1);}';
+const c=document.getElementById('c'),gl=c.getContext('webgl',{antialias:false,preserveDrawingBuffer:true});
+function sh(t,s){const o=gl.createShader(t);gl.shaderSource(o,s);gl.compileShader(o);
+ if(!gl.getShaderParameter(o,gl.COMPILE_STATUS)){document.body.insertAdjacentHTML('beforeend','<pre style="color:red;font:14px monospace">'+gl.getShaderInfoLog(o)+'</pre>');return o;}return o;}
+const pr=gl.createProgram();gl.attachShader(pr,sh(gl.VERTEX_SHADER,VS));gl.attachShader(pr,sh(gl.FRAGMENT_SHADER,FRAG));
+gl.linkProgram(pr);gl.useProgram(pr);
+const b=gl.createBuffer();gl.bindBuffer(gl.ARRAY_BUFFER,b);
+gl.bufferData(gl.ARRAY_BUFFER,new Float32Array([-1,-1,1,-1,-1,1,1,1]),gl.STATIC_DRAW);
+const l=gl.getAttribLocation(pr,'p');gl.enableVertexAttribArray(l);gl.vertexAttribPointer(l,2,gl.FLOAT,false,0,0);
+const U=n=>gl.getUniformLocation(pr,n);
+gl.uniform2f(U('u_res'),W,H); gl.uniform1f(U('u_time'),%(t)s);
+gl.uniform2f(U('u_mouse'),%(mx)s,%(my)s);
+gl.viewport(0,0,W,H); gl.drawArrays(gl.TRIANGLE_STRIP,0,4);
+const px=new Uint8Array(W*H*4); gl.readPixels(0,0,W,H,gl.RGBA,gl.UNSIGNED_BYTE,px);
+const out=document.createElement('canvas'); out.width=W; out.height=H; out.style.display='block';
+const ctx=out.getContext('2d'); const img=ctx.createImageData(W,H);
+for(let y=0;y<H;y++) img.data.set(px.subarray((H-1-y)*W*4,(H-y)*W*4), y*W*4);
+ctx.putImageData(img,0,0);
+c.remove(); document.body.appendChild(out);
+</script></body></html>"""
+
+def render(frag_path, out, t=0.0, w=640, h=640, mx=0.5, my=0.5):
+    src = open(frag_path).read().encode()
+    b64 = base64.b64encode(src).decode()
+    html = HTML % dict(w=w, h=h, t=t, mx=mx, my=my,
+                        frag="atob('%s')" % b64)
+    tmp = tempfile.NamedTemporaryFile("w", suffix=".html", delete=False)
+    tmp.write(html); tmp.close()
+    subprocess.run(["firefox", "--headless", "--new-instance", "--profile", "/tmp/ff2",
+                    "--window-size=%d,%d" % (w, h), "--screenshot=" + os.path.abspath(out),
+                    "file://" + tmp.name],
+                   env={**os.environ, "MOZ_NO_REMOTE": "1"},
+                   stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, timeout=120)
+    os.unlink(tmp.name)
+
+if __name__ == "__main__":
+    a = sys.argv[1:]
+    render(a[0], a[1], *(float(x) for x in a[2:]))
diff --git a/shot.py b/shot.py
new file mode 100755
index 0000000..ff5e644
--- /dev/null
+++ b/shot.py
@@ -0,0 +1,11 @@
+#!/usr/bin/env python3
+"""shot.py <page.html> <out.png> [t] [size]  — single still of a live page (uses its #shot mode)."""
+import os, subprocess, sys
+page, out = sys.argv[1], os.path.abspath(sys.argv[2])
+t = sys.argv[3] if len(sys.argv) > 3 else "0"
+w = sys.argv[4] if len(sys.argv) > 4 else "700"
+url = "file://" + os.path.abspath(page) + "#shot&t=%s&w=%s" % (t, w)
+subprocess.run(["firefox","--headless","--new-instance","--profile","/tmp/ff2",
+                "--window-size=%s,%s" % (w, w), "--screenshot=" + out, url],
+               env={**os.environ,"MOZ_NO_REMOTE":"1"},
+               stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, timeout=180)
diff --git a/test_ice.py b/test_ice.py
new file mode 100644
index 0000000..ccbdfa8
--- /dev/null
+++ b/test_ice.py
@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""Render regression checks. Requires Firefox and Pillow; the page itself needs neither."""
+import subprocess
+import tempfile
+import unittest
+from pathlib import Path
+from PIL import Image, ImageChops, ImageStat
+
+HERE = Path(__file__).resolve().parent
+
+
+class IceRenderTest(unittest.TestCase):
+    def test_loop_mouse_and_visible_plasma(self):
+        subprocess.run(['python3', str(HERE / 'build_plasma.py')], check=True)
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            profile = root / 'profile'
+            profile.mkdir()
+
+            def render(name, parameters):
+                output = root / (name + '.png')
+                url = (HERE / 'ice_plasma.html').as_uri() + '#shot&' + parameters
+                subprocess.run(['firefox', '--headless', '--new-instance', '--profile', str(profile),
+                                '--window-size=320,240', '--screenshot=' + str(output), url],
+                               check=True, timeout=120, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+                # Exclude the on-screen instructions.
+                with Image.open(output) as image:
+                    return image.convert('RGB').crop((0, 0, 320, 180))
+
+            start = render('start', 't=0&mx=0.5&my=0.5')
+            loop = render('loop', 't=30&mx=0.5&my=0.5')
+            moved = render('moved', 't=0&mx=0.9&my=0.5')
+            halfway = render('halfway', 't=15&mx=0.5&my=0.5')
+            difference = lambda a, b: sum(ImageStat.Stat(ImageChops.difference(a, b)).mean) / 3
+            self.assertLess(difference(start, loop), 1.0)
+            self.assertGreater(difference(start, moved), 3.0)
+            self.assertGreater(difference(start, halfway), 3.0)
+            self.assertGreater(ImageStat.Stat(start).stddev[2], 10.0)
+            luminance = start.convert('L').histogram()
+            pixels = sum(luminance)
+            self.assertLess(sum(luminance[:20]) / pixels, 0.10)  # No vast black voids.
+            self.assertGreater(sum(luminance[:35]) / pixels, 0.08)  # The depth stays dark.
+
+
+if __name__ == '__main__':
+    unittest.main()