Rik Cross, Senior Learning Manager here at the Raspberry Pi Foundation, shows you how to recreate the deadly explosions in the classic game, Bomberman.
An early incarnation of Bomberman on the NES; the series is still going strong today under Konami’s wing.
Creating Bomberman
Bomberman was first released in the early 1980s as a tech demo for a BASIC compiler, but soon became a popular series that’s still going today. Bomberman sees players use bombs to destroy enemies and uncover doors behind destructible tiles. In this article, I’ll show you how to recreate the bombs that explode in four directions, destroying parts of the level as well as any players in their path!
The game level is a tilemap stored as a two-dimensional array. Each tile in the map is a Tile object, which contains the tile type, and corresponding image. For simplicity, a tile can be set to one of five types; GROUND, WALL, BRICK, BOMB, or EXPLOSION. In this example code, BRICK and GROUND can be exploded with bombs, but WALL cannot, but of course, this behaviour can be changed.
Each Tile object also has a timer, which is decremented each frame of the game. When a tile’s timer reaches 0, an action is carried out, which is dependent on the tile type. BOMB tiles (and surrounding tiles) turn into EXPLOSION tiles after a short delay, and EXPLOSION tiles eventually turn back into GROUND. At the start of the game, the tilemap for the level is generated, in this case consisting of mostly GROUND, with some WALL and a couple of BRICK tiles. The player starts off in the top-left tile, and moves by using the arrow keys. Pressing the SPACE key will place a bomb in the player’s current tile, which is achieved by setting the Tile at the player’s position to BOMB. The tile’s timer is also set to a small number, and once this timer is decremented to 0, the bomb tile and the tiles around it are set to EXPLOSION.
Here’s Rik’s example code, which recreates Bomberman’s explosions in Python. To get it running on your system, you’ll first need to install Pygame Zero — you can find full instructions here. And you can download the code here.
The bomb explodes outwards in four directions, with a range determined by the RANGE, which in our code is 3. As the bomb explodes out to the right, for example, the tile to the right of the bomb is checked. If such a tile exists (i.e. the position isn’t out of the level bounds) and can be exploded, then the tile’s type is set to EXPLOSION and the next tile to the right is checked. If the explosion moves out of the level bounds, or hits a WALL tile, then the explosion will stop radiating in that direction. This process is then repeated for the other directions.
There’s a nice trick for exploding the bomb without repeating the code four times, and it relies on the sine and cosine values for the four direction angles. The angles are 0° (up), 90° (right), 180° (down) and 270° (left). When exploding to the right (at an angle of 90°), sin(90) is 1 and cos(90) is 0, which corresponds to the offset direction on the x- and y-axis respectively. These values can be multiplied by the tile offset, to explode the bomb in all four directions.
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