wiggle = love.graphics.newShader[[

  extern number seed;
  extern number amount;


  int grain = 10; //higher = less, lower = more

  float rand(vec2 co){
      return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
  }

	vec4 effect( vec4 color, Image texture, vec2 texture_coords, vec2 screen_coords) {
   		vec4 pixel_me = Texel(texture, texture_coords );

      return Texel(texture, texture_coords + (rand(texture_coords * seed) - .5) * amount);
      /*  		
        int resolution = int(12 * 1 / zoom);

        vec2 final_coords = floor((resolution * texture_coords) + 0.5) / resolution;

        vec4 averaged_pixel = (Texel(texture, final_coords - (1 / resolution)) + Texel(texture, final_coords)) / 2 + (rand(final_coords * seed) / grain);

        averaged_pixel.a = 1;

        pixel_me = Texel(texture, final_coords);

   		  return averaged_pixel;
      */
	}
]]

glow = love.graphics.newShader[[
      vec4 effect( vec4 color, Image texture, vec2 texture_coords, vec2 screen_coords) {
        vec4 pixel_me = Texel(texture, texture_coords );
        if (pixel_me.rgb != vec3(0,0,0))
          return pixel_me;
        
        int samples = 5;
        float intensity = 60;
        float radius = .1;

        for (int i = 1; i < samples; i++ ) {
          vec4 pixel_left = Texel(texture, texture_coords + vec2(-radius * i, 0)); 
          vec4 pixel_right = Texel(texture, texture_coords + vec2(radius * i, 0)); 
          vec4 pixel_top = Texel(texture, texture_coords + vec2(0, radius * i)); 
          vec4 pixel_bottom = Texel(texture, texture_coords + vec2(0, -radius * i));
          vec4 pixel_top_left = Texel(texture, texture_coords + vec2(-radius * i, radius * i)); 
          vec4 pixel_top_right = Texel(texture, texture_coords + vec2(radius * i, radius * i)); 
          vec4 pixel_bottom_left = Texel(texture, texture_coords + vec2(-radius * i, -radius * i)); 
          vec4 pixel_bottom_right = Texel(texture, texture_coords + vec2(radius * i, -radius * i));

          pixel_me += (pixel_left + pixel_right + pixel_top + pixel_bottom + pixel_bottom_right + pixel_bottom_left + pixel_top_right + pixel_top_left) / (intensity * i);

          intensity -= 2.5;

        }
        return pixel_me;
      }
    ]]

-- 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
-- a palette whose red, green, and yellow accents remain distinct for people
-- with deuteranopia.
accessibilityColorShader = love.graphics.newShader[[
  extern number accessibilityTime;

  vec3 rgbToHsv(vec3 c) {
    float maximum = max(c.r, max(c.g, c.b));
    float minimum = min(c.r, min(c.g, c.b));
    float delta = maximum - minimum;
    float hue = 0.0;

    if (delta > 0.0001) {
      if (maximum == c.r) {
        hue = mod((c.g - c.b) / delta, 6.0);
      } else if (maximum == c.g) {
        hue = ((c.b - c.r) / delta) + 2.0;
      } else {
        hue = ((c.r - c.g) / delta) + 4.0;
      }
      hue = hue / 6.0;
      if (hue < 0.0) hue += 1.0;
    }

    float saturation = maximum <= 0.0 ? 0.0 : delta / maximum;
    return vec3(hue, saturation, maximum);
  }

  vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 screen_coords) {
    vec4 pixel = Texel(texture, texture_coords) * color;
    vec3 hsv = rgbToHsv(pixel.rgb);

    // Preserve greys, white (including additive RGB overlap), and near-black
    // background detail.  Only colourful puzzle elements are recoloured.
    if (hsv.y < 0.22 || hsv.z < 0.06) return pixel;

    // Keep every additive pair in its own bucket.  In particular, magenta
    // (red + blue) must not become the same colour as red, and cyan
    // (green + blue) must not become the same colour as green.
    vec3 replacement;
    float pattern = 0.0;
    // Advance in whole pixels so the texture stays crisp instead of swimming.
    float ditherStep = floor(accessibilityTime * 1.5);
    if (hsv.x < 0.055 || hsv.x >= 0.94) {
      replacement = vec3(0.93, 0.18, 0.50); // red: pink
    } else if (hsv.x < 0.19) {
      replacement = vec3(1.00, 0.78, 0.08); // red + green: gold
      vec2 cell = mod(floor(screen_coords + vec2(ditherStep, 0.0)), vec2(9.0));
      pattern = length(cell - vec2(4.0)) < 1.6 ? 1.0 : 0.0; // dithered dots
    } else if (hsv.x < 0.43) {
      replacement = vec3(0.00, 0.72, 0.62); // green: turquoise
    } else if (hsv.x < 0.58) {
      replacement = vec3(0.12, 0.55, 0.96); // green + blue: sky blue
      pattern = mod(floor(screen_coords.x + screen_coords.y + ditherStep), 10.0) < 2.0 ? 1.0 : 0.0; // dithered slashes
    } else if (hsv.x < 0.77) {
      replacement = vec3(0.38, 0.32, 0.96); // blue: indigo
    } else {
      replacement = vec3(0.72, 0.25, 0.92); // red + blue: purple
      pattern = mod(floor((screen_coords.x + ditherStep) / 4.0) + floor(screen_coords.y / 4.0), 2.0); // dithered checker
    }

    // Secondary colours get a gently animated dither cue, so they are
    // identifiable even when their hue is hard to perceive.  Lighting and
    // fades remain.
    replacement = mix(replacement, vec3(1.0), pattern * 0.55);
    return vec4(replacement * hsv.z, pixel.a);
  }
]]