local WIDTH = 800
local HEIGHT = 600
local shader_code = [[
  extern vec2 screen_dims;
  extern number time;

  number pi = atan(1.0) * 4.0;

  vec4 effect(vec4 color, Image image, vec2 uvs, vec2 screen_coords) {
    vec2 screen_coords_norm = vec2(
        screen_coords.x / screen_dims.x,
        screen_coords.y / screen_dims.y
      );
    number y = 40 + sin(4.18 + 1.9 * time + pi * 8.3 * screen_coords_norm.x) * 10 +
     sin(screen_coords_norm.x * pi + time * 0.5) * cos(1.33 + pi * screen_coords_norm.x + pi * 0.7 * time) * 5;
    number y2 = 33 + y + sin(3.58 + 1.6 * time + pi * 5.2 * screen_coords_norm.x) * 11 +
     sin(time * 0.9) * cos(2.33 + pi * screen_coords_norm.x + pi * 1.9 * time) * 6;
    number y3 = 37 + y2 + sin(1.88 + 1.7 * time + pi * 6.5 * screen_coords_norm.x) * 12 +
     sin(time * 0.95) * cos(2.33 + pi * 2 * screen_coords_norm.x + pi * 1.2 * time) * 8;
    number y4 = 38 + y3 + sin(9.66 + 1.4 * time + pi * 5.1 * screen_coords_norm.x) * 10 +
     sin(time) * cos(5.33 + pi * 2 * screen_coords_norm.x + pi * 1.2 * time) * 12;
    number y5 = 44 + y4 + sin(1.66 + 2.4 * time + pi * 3.9 * screen_coords_norm.x) * 8 +
     sin(time * 0.8) * cos(1.88 + pi * 2.3 * screen_coords_norm.x + pi * 1.9 * time) * 11;
    number y6 = 37 + y5 + sin(2.11 + 3.0 * time + pi * 2.7 * screen_coords_norm.x) * 5 +
     sin(time * 0.82) * cos(6.19 + pi * 3.33 * screen_coords_norm.x + pi * 2.4 * time) * 14;

    if (screen_coords.y < screen_dims.y - y6) {
      return vec4(0.0, 0.0, 0.6, 1.0);
    } else if (screen_coords.y < screen_dims.y - y5) {
      return vec4(0.0, 0.0, 0.65, 1.0);
    } else if (screen_coords.y < screen_dims.y - y4) {
      return vec4(0.0, 0.0, 0.7, 1.0);
    } else if (screen_coords.y < screen_dims.y - y3) {
      return vec4(0.0, 0.0, 0.75, 1.0);
    } else if (screen_coords.y < screen_dims.y - y2) {
      return vec4(0.0, 0.0, 0.8, 1.0);
    } else if (screen_coords.y < screen_dims.y - y) {
      return vec4(0.0, 0.0, 0.85, 1.0);
    } else {
      return vec4(0.0, 0.0, 0.9, 1.0);
    }
  }
]]

function love.load()
  -- image_data = love.image.newImageData(WIDTH, HEIGHT)
  -- image = love.graphics.newImage(image_data)
  shader = love.graphics.newShader(shader_code)
end

local t = 0
function love.update(dt)
  t = t + dt
  shader:send("time", t)
end

function love.draw()
  love.graphics.setShader(shader)
  shader:send("screen_dims", {
    love.graphics.getWidth(),
    love.graphics.getHeight()
  })
  love.graphics.rectangle('fill', 0, 0, WIDTH, HEIGHT)
  love.graphics.setShader()
end

function love.keypressed(k)
  if k == "r" then love.event.quit "restart" end
end