GameDev Garden

Lua Essentials

You don’t need all of Lua. You need ~20% of it, used constantly. This page is that 20%. For the full language, the official Lua docs and Learn X in Y minutes are excellent — this hub just gives you the game-flavored cut.

1. Variables & printing

local score = 0
local playerName = "Marty"
score = score + 10
print(score) -- shows in console, great for debugging
 
-- print to game screen
function love.draw()
  love.graphics.print(string.format("Score: %d", score), 10, 10)
end

NOTE

Use local by default. Globals leak between files and cause spooky bugs in bigger games.

2. Conditionals & loops

if score > 100 then
  print("You win!")
end
 
for i = 1, 3 do
  print("count: " .. i)
end

3. Functions (your game verbs)

local function add(a, b)
  return a + b
end
 
score = add(score, 10)

Love2D itself is just functions it calls for you: love.load once, love.update(dt) every frame, love.draw() every frame. See Love2D Basics.

4. Tables (arrays + objects in one)

Tables are 90% of Lua. Learn them and everything clicks:

-- Array-like
local inventory = {"key", "map", "flux-capacitor"}
print(inventory[1]) -- prints "key" (Lua starts at 1!)
table.insert(inventory, "skateboard") -- appends to end
table.insert(inventory, 2, "lantern") -- insert at position 2, shifts rest right
local removed = table.remove(inventory, 3) -- removes + returns item at 3 ("map")
print(removed) -- prints "map" (the item we just removed)
 
-- Object-like
local player = { x = 100, y = 200, speed = 300 }
player.x = player.x + 10
 
-- Loop over it
for i, item in ipairs(inventory) do
  print(i, item)
end
 
-- pairs vs ipairs: ipairs is array-only, in order (1, 2, 3... stops at first nil).
-- pairs walks every key in any order, including object keys like x, y.
for k, v in pairs(player) do
  print(k, v) -- e.g. x  100 / y  200 / speed  300, order not guaranteed
end

5. The dt mindset

Games move per-frame, and frames aren’t constant. Multiply movement by dt (delta time, seconds since last frame):

-- BAD: speed depends on framerate
player.x = player.x + 5
-- GOOD: 300 pixels per second, every machine
player.x = player.x + 300 * dt

Try it (5 min)

In your main.lua, make a square move right at constant speed:

local x = 0
function love.update(dt)
  x = x + 200 * dt
end
function love.draw()
  love.graphics.rectangle("fill", x, 100, 50, 50)
end

Change 200 to 500 * dt vs 5 with no dt and feel the difference.

When it breaks

SymptomFix
attempt to index nilYou used a table that doesn’t exist yet — print() it right before the error line
unexpected symbol near '='Missing local/function keyword or an end above
Array starts at 0 habitLua arrays start at 1. myTable[0] is nil.

Next step

Continue with Love2D Basics — the 3 functions that run every game.

    Graph View

    Backlinks