Colours That Change

Part of the The Game Loop section of Coddy's Pygame journey. Lesson 12 of 35.

A colour is three numbers, so a variable can be one of them. Change the variable every frame and the colour changes on the screen.

glow = 0

while running:
    # events
    glow = (glow + 3) % 256
    pygame.draw.circle(screen, (255, glow, 0), (240, 180), 60)

Each frame adds 3 to the green part, so the circle turns from red through orange to yellow.

Every part of a colour must stay from 0 to 255. At 256 pygame stops with ValueError: invalid color. The % operator gives the remainder of a division: 256 % 256 is 0 and 258 % 256 is 2. So (glow + 3) % 256 starts again near 0 instead of passing 255, and the circle glows from red to yellow over and over.

Challenge

Easy

Make the circle glow from red to yellow.

Before the loop, set glow = 0.
In the loop, before drawing, add 3 to glow and keep it from 0 to 255 with % 256.
Draw the circle in (255, glow, 0).

Press Play: the circle glows from red to yellow, over and over. Then Check.

Try it yourself

import pygame

pygame.init()
screen = pygame.display.set_mode((480, 360))
pygame.display.set_caption("Glow")
clock = pygame.time.Clock()

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    screen.fill((30, 30, 46))
    pygame.draw.circle(screen, (255, 120, 0), (240, 180), 60)
    pygame.display.flip()
    clock.tick(60)

pygame.quit()