Spikes and Hearts

Part of the Worlds section of Coddy's Pygame journey. Lesson 32 of 35.

A game needs danger. The explorer has 3 lives, shown as hearts. Spikes and falling out of the cave each cost one.

Spikes fill only the lower half of their tile, so their Rect is the lower half: pygame.Rect(rect.x, rect.y + 18, TILE, 18). Draw the image 18 pixels higher, at the tile's corner.

Several dangers do the same thing: take a life and send the explorer back to the start. Give them one shared flag, and one block that acts on it:

hurt = False
if player.top > HEIGHT:
    hurt = True
for spike in spikes:
    if player.colliderect(spike):
        hurt = True
# later
if hurt:
    lives -= 1
    player.midbottom = start
    vel_y = 0

The hearts are three images in a row at the top left: full for each life left, empty for each lost.

for i in range(3):
    if i < lives:
        screen.blit(heart_img, (10 + i * 40, 8))
    else:
        screen.blit(heart_empty_img, (10 + i * 40, 8))

Challenge

Medium

Load spikes.png, heart.png and heart_empty.png into spikes_img, heart_img and heart_empty_img.
Make spikes = [] and lives = 3; for each ^, append the lower half Rect.
Replace the fall's reset with hurt = True; set hurt too when the player touches a spike. Put the if hurt: block after the coins.
Draw the spikes at (spike.x - camera_x, spike.y - 18) and the three hearts at the top left.

Try it yourself

import pygame

TILE = 36
WIDTH, HEIGHT = 576, 360
SPEED = 4
GRAVITY = 1
JUMP = -15
MAX_FALL = 12

LEVEL = [
    "................................................................",
    "................................................................",
    "................................................................",
    "................................................................",
    "#..............................................................#",
    "#....................C.........................#####...........#",
    "#......CC...C................CC.....CC.........#####.....CC....#",
    "#....................#.........................D...............#",
    "#.P.........#...E....#...^.......K......E......D.C....^......F.#",
    "#######..####################..##########################..#####",
]

pygame.init()
screen = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("Moss Caves")
clock = pygame.time.Clock()
font = pygame.font.Font("assets/fonts/pixel.ttf", 24)


def load(name):
    return pygame.image.load("assets/images/" + name).convert_alpha()


background = pygame.image.load("assets/backgrounds/forest.png").convert_alpha()
grass_img = load("grass.png")
grass_left_img = load("grass_left.png")
grass_right_img = load("grass_right.png")
dirt_img = load("dirt.png")
player_img = load("player.png")
coin_img = load("coin.png")


def solid(row, col):
    if row < 0 or row >= len(LEVEL) or col < 0 or col >= len(LEVEL[0]):
        return False
    return LEVEL[row][col] == "#"


walls = []
tiles = []
coins = []
for row, line in enumerate(LEVEL):
    for col, char in enumerate(line):
        rect = pygame.Rect(col * TILE, row * TILE, TILE, TILE)
        if char == "#":
            if solid(row - 1, col):
                image = dirt_img
            elif not solid(row, col - 1) and solid(row, col + 1):
                image = grass_left_img
            elif solid(row, col - 1) and not solid(row, col + 1):
                image = grass_right_img
            else:
                image = grass_img
            walls.append(rect)
            tiles.append((image, rect))
        elif char == "P":
            start = rect.midbottom
        elif char == "C":
            coins.append(rect)

level_width = len(LEVEL[0]) * TILE
player = player_img.get_rect(midbottom=start)
vel_y = 0
on_ground = False
camera_x = 0
coins_collected = 0

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.KEYDOWN and event.key in (pygame.K_SPACE, pygame.K_UP):
            if on_ground:
                vel_y = JUMP
        elif event.type == pygame.KEYUP and event.key in (pygame.K_SPACE, pygame.K_UP):
            if vel_y < -4:
                vel_y = -4

    keys = pygame.key.get_pressed()
    dx = 0
    if keys[pygame.K_LEFT]:
        dx -= SPEED
    if keys[pygame.K_RIGHT]:
        dx += SPEED

    player.x += dx
    for wall in walls:
        if player.colliderect(wall):
            if dx > 0:
                player.right = wall.left
            elif dx < 0:
                player.left = wall.right

    vel_y = min(vel_y + GRAVITY, MAX_FALL)
    player.y += vel_y
    on_ground = False
    for wall in walls:
        if player.colliderect(wall):
            if vel_y > 0:
                player.bottom = wall.top
                on_ground = True
            elif vel_y < 0:
                player.top = wall.bottom
            vel_y = 0

    if player.top > HEIGHT:
        player.midbottom = start
        vel_y = 0

    for coin in coins[:]:
        if player.colliderect(coin):
            coins.remove(coin)
            coins_collected += 1

    camera_x = player.centerx - WIDTH // 2
    camera_x = max(0, min(camera_x, level_width - WIDTH))

    shift = camera_x // 3 % 72
    for y in range(0, HEIGHT, 72):
        for x in range(-shift, WIDTH, 72):
            screen.blit(background, (x, y))
    for image, rect in tiles:
        screen.blit(image, (rect.x - camera_x, rect.y))
    for coin in coins:
        screen.blit(coin_img, (coin.x - camera_x, coin.y))
    screen.blit(player_img, (player.x - camera_x, player.y))
    text = font.render(f"Coins: {coins_collected}", True, (255, 255, 255))
    screen.blit(text, text.get_rect(topright=(WIDTH - 12, 14)))
    pygame.display.flip()
    clock.tick(60)

pygame.quit()