Gem Under the Crate

Part of the The Game Loop section of Coddy's Pygame journey. Lesson 19 of 35.

Now the crate becomes the game. Each gem appears under the crate: drag the crate off and click the gem, and the crate moves onto the next one.

A Rect has a center, the point in its middle. Give one Rect another's centre and it sits right on top of it, whatever their sizes:

gem = pygame.Rect(300, 120, 30, 30)
crate = pygame.Rect(0, 0, 60, 60)
crate.center = gem.center

Only crate moves, to (285, 105, 60, 60). Do this once before the loop for the first gem, and again each time a gem gets a new place.

Challenge

Easy

Hide each gem under the crate.

Right after making crate, set crate.center = gem.center.
In the gem branch, after the new gem.y, set crate.center = gem.center again.

Press Play, drag the crate off and click the gem: the crate jumps onto the next one. Then Check.

Try it yourself

import random
import pygame

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

gem = pygame.Rect(225, 165, 30, 30)
crate = pygame.Rect(40, 230, 60, 60)
dragging = False
score = 0

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.MOUSEBUTTONDOWN:
            if crate.collidepoint(event.pos):
                dragging = True
            elif gem.collidepoint(event.pos):
                score += 1
                gem.x = random.randint(15, 435)
                gem.y = random.randint(55, 315)
        elif event.type == pygame.MOUSEBUTTONUP:
            dragging = False
        elif event.type == pygame.MOUSEMOTION and dragging:
            crate.move_ip(event.rel)

    screen.fill((30, 30, 46))
    gem_points = [gem.midtop, gem.midright, gem.midbottom, gem.midleft]
    pygame.draw.polygon(screen, (80, 220, 255), gem_points)
    if gem.collidepoint(pygame.mouse.get_pos()):
        pygame.draw.rect(screen, (255, 196, 0), gem.inflate(10, 10), 2)
    pygame.draw.rect(screen, (150, 100, 50), crate)
    pygame.draw.rect(screen, (110, 70, 35), crate, 3)
    for i in range(score):
        pygame.draw.rect(screen, (240, 110, 180), (10 + 10 * i, 14, 8, 8))
    mouse_x, mouse_y = pygame.mouse.get_pos()
    pygame.draw.circle(screen, (240, 240, 240), (mouse_x, mouse_y), 10, 2)
    pygame.display.flip()
    clock.tick(60)

pygame.quit()