patterns — split

def g15_split(rng):
    """Each cell is flat, halved or quartered — two ramp steps per cell."""
    steps = rng.randint(5, 8)
    N = rng.choice([25, 30, 40])
    c = Canvas(N, _pal(rng), steps, "split", "squares")
    f = Field(rng, "mesh", warp=rng.uniform(0.2, 0.4), steps=steps)
    c.ground_from(f)
    C = c.C
    for j in range(N):
        for i in range(N):
            u, v = c.uv(i, j)
            k = f.idx(u, v)
            lo = min(steps - 1, k + 1)
            x, y = i * C, j * C
            mode = (i * 7 + j * 3 + k) % 4
            if mode == 1:
                c.sq(x, y + C / 2, C, C / 2, lo)
            elif mode == 2:
                c.sq(x + C / 2, y, C / 2, C, lo)
            elif mode == 3:
                c.sq(x, y, C / 2, C / 2, lo)
                c.sq(x + C / 2, y + C / 2, C / 2, C / 2, lo)
    return c