Love2d Core

LÖVE (Love2D) Core

Set up and debug the foundation of a LÖVE game in Lua: the callback loop, frame-rate- independent movement, input, and screen states. Targets LÖVE 11.5.

When to use

• Use when starting a LÖVE game, wiring up main.lua/conf.lua, or fixing the core loop, movement that runs at the wrong speed, input handling, or screen switching.
• Use when the workspace has main.lua calling love.*, a conf.lua, or a .love file.

*When not to use: Lua language* questions unrelated to LÖVE; physics bodies/joints (LÖVE uses Box2D via love.physics — a separate concern); shader code (love.graphics GLSL is its own topic). For cross-engine save/load patterns, use save-systems.

Core workflow

1. Confirm the entry points. A LÖVE game runs main.lua; it should define love.load() (one-time setup), love.update(dt) (state), and love.draw() (rendering). Window/version setup goes in conf.lua (run before modules load).
2. Pin the version. Set t.version = "11.5" in conf.lua so LÖVE warns on mismatch.
3. Drive all motion by `dt` (delta time, in seconds) so speed is frame-rate independent.
4. Handle input two ways: polled (love.keyboard.isDown in update, for held keys) and event (love.keypressed callback, for discrete presses).
5. Manage screens (menu, game, pause) with a small state stack rather than a pile of if flags — see Patterns and references/state-stack.md.
6. Run and observe. Launch with love . from the project folder; verify the window, motion speed, and input on screen before assuming it works.

Patterns

1. main.lua skeleton (the callback loop + input)

-- main.lua — LÖVE calls these callbacks for you. Colors are 0–1 in LÖVE 11.x.
function love.load()
    -- One-time setup. speed is in PIXELS PER SECOND, not per frame.
    player = { x = 100, y = 100, size = 40, speed = 220 }
    love.graphics.setBackgroundColor(0.1, 0.1, 0.12)
end

function love.update(dt)
    -- Polled input: good for continuous movement while a key is held.
    if love.keyboard.isDown("right") then player.x = player.x + player.speed * dt end
    if love.keyboard.isDown("left")  then player.x = player.x - player.speed * dt end
    if love.keyboard.isDown("down")  then player.y = player.y + player.speed * dt end
    if love.keyboard.isDown("up")    then player.y = player.y - player.speed * dt end
end

function love.draw()
    love.graphics.setColor(0.2, 0.8, 1.0)                 -- tint ON
    love.graphics.rectangle("fill", player.x, player.y, player.size, player.size)
    love.graphics.setColor(1, 1, 1)                       -- reset tint before text/images
    love.graphics.print("Arrow keys to move, Esc to quit", 10, 10)
end

function love.keypressed(key)
    -- Event input: fires once per physical press. Use for menus, jumps, toggles.
    if key == "escape" then love.event.quit() end
end

2. Frame-rate independence (the single most common bug)

-- RIGHT: scaled by dt → same real-world speed at 30 or 240 FPS.
player.x = player.x + player.speed * dt
-- WRONG: "pixels per frame" → moves twice as fast at double the frame rate.
player.x = player.x + player.speed

3. conf.lua (window + version; runs before main.lua)

-- conf.lua — must be its own file; love.conf will NOT run from main.lua.
function love.conf(t)
    t.version = "11.5"             -- the LÖVE version this game targets (string "X.Y")
    t.window.title  = "My LÖVE Game"
    t.window.width  = 800
    t.window.height = 600
    t.window.vsync  = 1            -- number since 11.0: 1 = on, 0 = off, -1 = adaptive
    t.window.resizable = false
    t.modules.physics = false      -- disable modules you don't use to trim startup/memory
end

4. Color is 0–1 in LÖVE 11.x (not 0–255)

-- LÖVE 11.x uses normalized floats. (Pre-11.0 code used 0–255 and will look wrong.)
love.graphics.setColor(1, 0, 0)                          -- opaque red
love.graphics.setColor(0.2, 0.8, 1.0, 0.5)               -- translucent cyan (alpha 0.5)
-- Need to convert old byte values? Use the helper instead of dividing by hand:
love.graphics.setColor(love.math.colorFromBytes(128, 234, 255))

5. Screen states (brief — full manager in references)

-- A screen is a table with optional :update(dt), :draw(), :keypressed(key).
-- Keep the active screen on a stack so pause/menu overlays are trivial to pop.
local Stack = require("state_stack")   -- see references/state-stack.md for the module
function love.load()              Stack.push(require("screens.menu")) end
function love.update(dt)          Stack.current():update(dt) end
function love.draw()              Stack.current():draw() end
function love.keypressed(key)     Stack.current():keypressed(key) end

Pitfalls

• Speed varies with FPS → you forgot * dt. Every per-frame change to position, timers, or animation must be scaled by dt.
• `love.conf` placed in `main.lua` → it silently does nothing. It must live in conf.lua, which LÖVE runs before loading modules.
• Colors washed out or invisible → you used 0–255 values. In 11.x, setColor(255,0,0) clamps to white; use setColor(1,0,0) or love.math.colorFromBytes.
• Everything tinted after one `setColor` → color is global and persists across draws. Reset with love.graphics.setColor(1, 1, 1) before drawing text/images you want untinted.
• Nothing happens on key release/repeat → love.keypressed(key, scancode, isrepeat) fires on press (and OS key-repeat); use love.keyreleased for release, and check isrepeat if you must ignore held-key repeats.

References

• For a complete push/pop screen-state manager (menu → game → pause, with delegated callbacks), read references/state-stack.md.

Related skills

• save-systems — saving/loading game state (engine-agnostic).
• input-systems — rebindable, multi-device input architecture.
• pygame-core / phaser-core — the same loop concepts in other lightweight engines.