"""Lichen on stone
Diffusion-limited aggregation: wanderers drift at random until they touch the
colony, and now and then one stays. Seeded with 17, the number of seconds between sshd first
starting on eske and the first stranger knocking. Old growth is dark; each new
arrival is paler, and the newest tips come out orange, like Xanthoria.
Planted 2026-09-23 by the second session.
"""
import math
import random
import sys

W = H = 160
N = 6000
STICK = 0.06  # well below 1: wanderers slip past tips and fill in, so growth is lobed, not feathery
rng = random.Random(17)

grid = [[False] * W for _ in range(H)]
cx, cy = W // 2, H // 2
# three colonies near the middle; they grow toward each other (in 2026-09 they had not yet met)
seeds = [(cx - 22, cy - 10), (cx + 20, cy - 16), (cx + 2, cy + 22)]
for sx, sy in seeds:
    grid[sy][sx] = True
stuck = list(seeds)
radius = 30.0
STEPS = ((1, 0), (-1, 0), (0, 1), (0, -1))


def touching(x, y):
    for dx in (-1, 0, 1):
        for dy in (-1, 0, 1):
            if (dx or dy) and grid[y + dy][x + dx]:
                return True
    return False


while len(stuck) < N:
    a = rng.uniform(0, 2 * math.pi)
    r0 = radius + 4
    x, y = int(cx + r0 * math.cos(a)), int(cy + r0 * math.sin(a))
    while True:
        dx, dy = rng.choice(STEPS)
        x, y = x + dx, y + dy
        d = math.hypot(x - cx, y - cy)
        if d > radius + 12 or not (1 <= x < W - 1 and 1 <= y < H - 1):
            break  # wandered off; let another come
        if touching(x, y) and not grid[y][x] and rng.random() < STICK:
            grid[y][x] = True
            stuck.append((x, y))
            radius = max(radius, d)
            break
    if radius > W / 2 - 8:
        break


def lerp(c1, c2, t):
    return "#%02x%02x%02x" % tuple(round(a + (b - a) * t) for a, b in zip(c1, c2))


S = 3  # px per cell
out = [f'<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 {W*S} {H*S}" width="{W*S}" height="{H*S}">',
       '<defs><radialGradient id="stone" cx="45%" cy="40%" r="75%">'
       '<stop offset="0" stop-color="#8d8a82"/><stop offset="1" stop-color="#55534e"/></radialGradient></defs>',
       f'<rect width="{W*S}" height="{H*S}" fill="url(#stone)"/>']
# a little grit on the stone
for _ in range(900):
    gx, gy = rng.uniform(0, W * S), rng.uniform(0, H * S)
    out.append(f'<circle cx="{gx:.1f}" cy="{gy:.1f}" r="{rng.uniform(.4, 1.6):.1f}" '
               f'fill="{rng.choice(("#6b6861", "#a19e95", "#45433e"))}" opacity=".7"/>')
n = len(stuck)
moss, pale, orange = (52, 74, 40), (190, 204, 150), (224, 132, 38)
for i, (x, y) in enumerate(stuck):
    t = i / n
    col = lerp(moss, pale, t / 0.88) if t < 0.88 else lerp(pale, orange, min(1, (t - 0.88) / 0.08))
    out.append(f'<circle cx="{x*S+1.5}" cy="{y*S+1.5}" r="{S*0.72:.2f}" fill="{col}"/>')
out.append("</svg>")
sys.stdout.write("\n".join(out))