rusterix 0.9.1

Rusterix is the game engine of Eldiron.
Documentation 
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fn hash21(p)
{
	let p3 = fract(p * vec3(.1031, .1030, .0973));
	p3 += dot(p3, p3.yzx + 33.33);
    return fract((p3.xx+p3.yz)*p3.zy);
}

fn s_box(p, b, rf) {
    let q = abs(p) - b + rf;
    return length(max(q, 0.0)) + min(max(q.x, q.y), 0.0) - rf;
}

fn shade() {

    let gap = 0.1;
    let rotation = 2;
    let rounding = 0.04;

    uv = uv % 1;

    let p = uv;
    let ip = floor(uv);
    p -= ip;

    let last_l = 0.0;
    let l = vec2(1.0, 1.0);
    let r = hash21(ip);

    for (let i = 0; i < 6; i += 1) {
        r = fract(dot(l + r, vec2(123.71, 439.43))) * 0.4 + (1.0 - 0.4) / 2.0;

        last_l = l;
        if l.x > l.y {
            p = vec2(p.y, p.x);
            l = vec2(l.y, l.x);
        }

        if p.x < r {
            l.x /= r;
            p.x /= r;
        } else {
            l.x /= 1.0 - r;
            p.x = (p.x - r) / (1.0 - r);
        }

        if last_l.x > last_l.y {
            p = vec2(p.y, p.x);
            l = vec2(l.y, l.x);
        }
    }
    p -= 0.5;

    // Create the id
    let id = hash21(ip + l);

    // Slightly rotate the tile based on its id
    p = rotate2d(p, (id - 0.5) * rotation);

    // Gap, or mortar, width. Using "l" to keep it roughly constant.
    let th = l * 0.02 * gap;

    // Take the subdivided space and turn them into rounded pavers.
    let c = s_box(p, 0.5 - th, rounding);

    let c01 = clamp(0.5 - c / (2.0 * 0.5), 0.0, 1.0);

    let mask = 1.0;
    if c > 0.0 {
        mask = 0.0;
    }
    color = vec3(mask.x, id.x, c01.x);
}