The Game Loop

Every game runs in a loop that continuously updates and renders the game state. Understanding this loop is fundamental to game development.

How Games Work

A game loop typically does three things every frame:

1. Process input - Check for keyboard/mouse input
2. Update - Move objects, check collisions, update game state
3. Draw - Render everything to the screen

This happens 60 times per second (or more), creating the illusion of movement.

Delta Time (dt)

The love.update(dt) function receives a parameter called dt (delta time). This is the time in seconds since the last frame.

Why is this important?

If we move our player by a fixed amount each frame, the game runs differently on fast vs slow computers. Using dt makes movement consistent:

luaRun in Sandbox
-- Bad: Speed depends on framerate
x = x + 5

-- Good: Speed is consistent regardless of framerate
x = x + speed * dt

Practical Example

Let's create a simple animation using the game loop. We'll make a circle move across the screen:

luaRun in Sandbox
function love.load()
    -- Starting position
    x = 0
    y = 150
    speed = 100  -- pixels per second
end

function love.update(dt)
    -- Move right by speed * dt pixels
    x = x + speed * dt

    -- Wrap around when we go off screen
    if x > 400 then
        x = -20
    end
end

function love.draw()
    -- Draw a white circle at (x, y)
    love.graphics.setColor(1, 1, 1)
    love.graphics.circle("fill", x, y, 20)
end

Key Concepts:

• love.graphics.setColor(r, g, b) sets the drawing color (values from 0 to 1)
• love.graphics.circle("fill", x, y, radius) draws a filled circle
• dt ensures smooth, consistent movement

Try it! Watch the circle move across the screen. Try changing the speed value!