Why This One Bit of Code Runs Everything You See, Hear, and Do in a Game
When you play a game, everything feels smooth: the character jumps when you press a button, the enemies move, music plays, health bars update, and the world reacts in real-time.
But behind all that? There’s one unsung hero doing the heavy lifting: the game loop.
At Codexa, we love unpacking what makes games tick literally. So let’s dive into what a game loop is, how it works, and why it’s one of the most important systems in any game, from the tiniest indie platformer to the most complex open-world RPG.
What Is a Game Loop?
At its core, a game loop is a cycle that runs continuously while the game is running. It’s the heartbeat of your game. It checks for input, updates the game’s state, and then renders the result—over and over again, usually 60 times per second (or more).
If you break it down, the simplest loop looks like this:
pythonCopyEditwhile game_is_running:
process_input()
update_game_state()
render_to_screen()
Each part of this loop is responsible for a critical piece of gameplay. It might seem basic, but this loop is what makes a game feel alive.
1. Processing Input
This is where the game listens to the player:
- Is a key pressed?
- Did the mouse move?
- Is the gamepad tilted?
- Did someone tap the screen?
Your inputs jumping, shooting, moving, selecting—are all caught here. The game loop grabs them in real time and passes them to the systems that need to respond.
2. Updating the Game State
This is where the magic happens.
The game loop now takes everything it knows (from player inputs, AI behavior, physics systems, etc.) and updates the game’s state.
That includes:
- Character positions
- Enemy movement and logic
- Physics (like gravity or collisions)
- Health and scores
- Game timers
- Event triggers
Everything you see in the world—things moving, changing, reacting—is updated during this phase. Without it, your game would be static and unresponsive.
3. Rendering the Frame
Finally, the updated game world is drawn to the screen.
- Sprites are rendered in 2D games
- 3D models are shaded and lit
- UI elements are drawn
- Visual effects like particles and lighting are added
This is where all the calculations and logic come to life visually. And then—guess what?—the loop starts again.
Timing & Frame Rates: Why Speed Matters
The game loop usually runs every 1/60th of a second—that’s 60 frames per second (FPS). But in reality, things can get tricky:
- Too slow, and your game feels laggy or unresponsive.
- Too fast, and physics can break or animations might run too quickly.
That’s why many games use delta time a way to measure the time between each loop and adjust calculations accordingly.
pythonCopyEditdelta_time = current_time - last_frame_time
This makes movement, physics, and animations consistent, no matter the frame rate.
Fixed vs. Variable Game Loops
There are different styles of game loops:
- Fixed timestep: Updates happen at a steady rate (great for physics-heavy games).
- Variable timestep: Updates adapt to performance (easier to implement but less consistent).
- Hybrid: A mix, using fixed steps for simulation and variable steps for rendering.
Game engines like Unity and Unreal use complex versions of the loop behind the scenes but at the heart of it, it’s all the same cycle.
Why You Should Care (Even If You’re Not a Coder)
Understanding the game loop helps you:
- Design better gameplay: You’ll know how and when things happen.
- Debug smarter: You’ll understand timing issues and performance bugs.
- Write cleaner code: Especially for updates, AI, and movement systems.
- Appreciate game feel: Smooth input and timing depend on a healthy loop.
Even if you’re more of a designer or artist, grasping this one system helps you collaborate better with devs and see how your work gets brought to life in-game.
Final Thoughts from Codexa
The game loop is the invisible engine that keeps everything moving. It’s the rhythm of your controls, the pace of your world, and the timing of your story. Miss it, and the game breaks. Nail it, and players never even realize it’s there.
So whether you’re writing your first Pong clone or building the next big open-world hit, remember:
It all starts with a loop.
Codexa 