Add directional sticky and skewer box variants

shaders.lua

@@ -59,6 +59,53 @@ glow = love.graphics.newShader[[
       }
     ]]
 
+-- Sticky boxes reuse the authored box textures. This shader only wobbles their
+-- sampling; the draw helper adds a tiny squash-and-stretch bounce around center.
+goopShader = love.graphics.newShader[[
+  extern number goopTime;
+  extern vec2 sourceSize;
+
+  float goopHash(float value) {
+    return fract(sin(value * 91.3458) * 47453.5453);
+  }
+
+  vec4 effect(vec4 color, Image texture, vec2 textureCoords, vec2 screenCoords) {
+    float sourceY = textureCoords.y;
+    float pixelWidth = 1.0 / sourceSize.x;
+    float pixelHeight = 1.0 / sourceSize.y;
+    float column = floor(textureCoords.x * sourceSize.x / 2.0);
+    float seed = goopHash(column);
+
+    // Two gentle, out-of-phase waves make the surface feel soft and viscous.
+    // Both stay sub-pixel so the authored silhouette remains recognizable.
+    float horizontalWave = sin(goopTime * 1.7 + sourceY * 10.0 + seed * 6.2831);
+    float verticalWave = sin(goopTime * 1.3 + textureCoords.x * 12.0 + seed * 3.1415);
+    float sourceX = clamp(textureCoords.x + horizontalWave * pixelWidth * 0.45,
+                          pixelWidth * 0.5, 1.0 - pixelWidth * 0.5);
+    float wobbledY = clamp(sourceY + verticalWave * pixelHeight * 0.28,
+                           pixelHeight * 0.5, 1.0 - pixelHeight * 0.5);
+
+    return Texel(texture, vec2(sourceX, wobbledY)) * color;
+  }
+]]
+
+function drawGoopySprite(sprite, x, y, scale)
+	local w, h = sprite:getWidth(), sprite:getHeight()
+	local time = love.timer.getTime()
+	local bounce = math.sin(time * 2.4 + w * .17 + h * .11) * .035
+	local scaleX = scale * (1 + bounce)
+	local scaleY = scale * (1 - bounce)
+	local drawX = x - w * (scaleX - scale) / 2
+	local drawY = y - h * (scaleY - scale) / 2
+
+	goopShader:send("goopTime", time)
+	goopShader:send("sourceSize", {w, h})
+	local previousShader = love.graphics.getShader()
+	love.graphics.setShader(goopShader)
+	love.graphics.draw(sprite, drawX, drawY, 0, scaleX, scaleY)
+	love.graphics.setShader(previousShader)
+end
+
 -- Accessibility post-process.  The puzzle's RGB channels are normally also
 -- its visual language, so this runs only after the entire scene has been
 -- composed.  It leaves neutral UI/text alone and remaps saturated colours to