Edge Tiles

Part of the Worlds section of Coddy's Pygame journey. Lesson 8 of 35.

A platform looks finished when its ends are rounded. The pack has grass_left.png and grass_right.png for the two ends of a grassy surface.

Now each tile looks at three neighbours: above, left and right. Some of them are outside the map, at the edges. A helper function answers for any position, inside or not:

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] == "#"

Outside the map counts as empty. With the helper, the choice reads like the rule:

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
tiles.append((image, pygame.Rect(x, y, TILE, TILE)))

A tile with ground on both sides, or on neither side, keeps the plain grass. At the map's left edge, column 0, the tile to the left is outside, so it counts as empty and the ground there starts with grass_left_img.

Challenge

Medium

The starter loads grass_left.png into grass_left_img and grass_right.png into grass_right_img.

Write a function solid(row, col) that returns False outside the map and LEVEL[row][col] == "#" inside it.
For each #: dirt_img when the tile above is solid; else grass_left_img when only the right neighbour is solid; else grass_right_img when only the left neighbour is solid; else grass_img.

Try it yourself

import pygame

TILE = 36

LEVEL = [
    "###.............",
    "###.............",
    "..........C.....",
    ".........####...",
    "..C.............",
    ".####......C....",
    "..........###...",
    "#....C.........#",
    "###..##...###.##",
    "######..########",
]

pygame.init()
screen = pygame.display.set_mode((576, 360))
pygame.display.set_caption("Tiles")
clock = pygame.time.Clock()

grass_img = pygame.image.load("assets/images/grass.png").convert_alpha()
grass_left_img = pygame.image.load("assets/images/grass_left.png").convert_alpha()
grass_right_img = pygame.image.load("assets/images/grass_right.png").convert_alpha()
dirt_img = pygame.image.load("assets/images/dirt.png").convert_alpha()
coin_img = pygame.image.load("assets/images/coin.png").convert_alpha()

tiles = []
for row, line in enumerate(LEVEL):
    for col, char in enumerate(line):
        x, y = col * TILE, row * TILE
        if char == "#":
            if row == 0 or LEVEL[row - 1][col] != "#":
                image = grass_img
            else:
                image = dirt_img
            tiles.append((image, pygame.Rect(x, y, TILE, TILE)))
        elif char == "C":
            tiles.append((coin_img, pygame.Rect(x, y, TILE, TILE)))

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

    screen.fill((140, 200, 240))
    for image, rect in tiles:
        screen.blit(image, rect)
    pygame.display.flip()
    clock.tick(60)

pygame.quit()