import zlib
import struct


def png_chunk(chunk_type: bytes, data: bytes) -> bytes:
    return (
        struct.pack(">I", len(data))
        + chunk_type
        + data
        + struct.pack(">I", zlib.crc32(chunk_type + data) & 0xFFFFFFFF)
    )


def create_png(width: int, height: int, pixels: list) -> bytes:
    """Create a PNG from a 2D list of (R, G, B) tuples."""
    raw = bytearray()
    for row in pixels:
        raw.append(0)  # no filter
        for r, g, b in row:
            raw.extend((r, g, b))
    compressed = zlib.compress(bytes(raw), 9)

    ihdr_data = struct.pack(">IIBBBBB", width, height, 8, 2, 0, 0, 0)
    ihdr = png_chunk(b"IHDR", ihdr_data)
    idat = png_chunk(b"IDAT", compressed)
    iend = png_chunk(b"IEND", b"")

    return b"\x89PNG\r\n\x1a\n" + ihdr + idat + iend


BLUE = (37, 99, 235)
WHITE = (255, 255, 255)
SIZE = 64

pixels = []
for y in range(SIZE):
    row = []
    for x in range(SIZE):
        dx = x - SIZE // 2
        dy = y - SIZE // 2
        dist = (dx * dx + dy * dy) ** 0.5
        if dist < SIZE * 0.25:
            row.append(WHITE)
        else:
            row.append(BLUE)
    pixels.append(row)

with open("icon.png", "wb") as f:
    f.write(create_png(SIZE, SIZE, pixels))

print("Generated icon.png")