ParallaxLayer

pos Vector2 optional

Where the middle of the image is in the world when the camera is there too

size Vector2 optional

World size of one copy of the image

parallax number|Vector2 optional, default 0.5

How much of the camera's movement it follows, 0 stays with the world and 1 with the screen, a Vector2 to follow x and y by different amounts

renderOrder number optional

Low to draw behind the game, far layers lowest

drawFunction function optional

Draws the image, given the canvas context, its size in pixels and the layer; mountains when not given; called once when the layer is made and on redraw(), not each frame, so it draws with the canvas 2D context, not the engine's draws like drawTile

canvasSize Vector2 optional

Size of the image in pixels

// three ranges of mountains, the far ones lighter and slower
for (let i = 3; i--;)
    new ParallaxLayer(vec2(0, i*2), vec2(40, 20), .9 - i*.2, -1e3 + i,
        parallaxMountains(hsl(.6, .3, .7 - i*.2), hsl(.6, .5, .2), i));

// or draw your own image into the layer
new ParallaxLayer(vec2(), vec2(40, 20), .5, -1e3, (context, size)=>
{
    context.fillStyle = '#fff';
    context.fillRect(size.x/2 - 20, size.y/2 - 20, 40, 40);
});