A mainloop for games

by Peter Stuifzand

Every game contains a mainloop. The mainloop is the center of all the action in a game. But how is a mainloop structured?

Introduction

In the most general sense a game is structured around three parts: startup, the mainloop and shutdown. In this article we will look at the structure of the mainloop in games.

Structure of the mainloop

A mainloop is a simple loop that goes on until some condition is met.

// .. startup code

for (;;) {
    handle_input();
    update_game_state();
    draw_gfx();
}

// .. shutdown code

In most games the mainloop looks like this. It's about as simple as you can get.

Input handling

The best way to handle input is to set a variable for each possible key press. In a sidescrolling game it's easiest to set a speed for left and right movement when the appropriate key is pressed.

The x and y coordinate of the unit can be updated in the update_game_state function.

Update the game state

Based on input of the previous step we are now able to calculate the differences to the game world.