"""16x16 bouncing pixel with fading trail."""

from machine import Pin
import neopixel
import time

from panel16_utils import PANEL_H, PANEL_W, clamp8, xy_to_index


np = neopixel.NeoPixel(Pin(4), PANEL_W * PANEL_H)

trail = [[0 for _ in range(PANEL_W)] for _ in range(PANEL_H)]
x = 0
y = 0
vx = 1
vy = 1

for _frame in range(420):
    for yy in range(PANEL_H):
        for xx in range(PANEL_W):
            trail[yy][xx] = max(0, trail[yy][xx] - 14)

    trail[y][x] = 255

    for yy in range(PANEL_H):
        for xx in range(PANEL_W):
            v = trail[yy][xx]
            np[xy_to_index(xx, yy)] = (clamp8(v), clamp8(v // 2), clamp8(30))

    np.write()
    time.sleep(0.02)

    x += vx
    y += vy
    if x <= 0 or x >= PANEL_W - 1:
        vx *= -1
    if y <= 0 or y >= PANEL_H - 1:
        vy *= -1

np.fill((0, 0, 0))
np.write()