Variables — remembering things

Scripts that can't remember anything are useless. Right now your scripts read a line, do a thing, and forget it. This lesson gives your scripts a memory: variables.

#What a variable is

A variable is a named box. You put something in it, and later you can take it out or swap what's inside. "Box" is the right mental model — the box has a name, and the contents can change.

local coins = 0

Read that as: "make a box called coins, and put the number 0 in it."

The word local means "this box exists only inside this part of the script" — you'll use it on every variable. It keeps your script tidy and prevents surprises. Just write local every time.

#Using the box

Once a box exists, you can read it and change it:

local coins = 0

print(coins)      --> 0

coins = 5         -- put a new number in the box
print(coins)      --> 5

coins = coins + 1 -- take what's in the box, add 1, put it back
print(coins)      --> 6

That last line is worth sitting with: coins = coins + 1 reads the box, does math, and stores the result back in the same box. It's how you'll count almost everything in Roblox — kills, clicks, coins.

local lives = 3
lives = lives - 1
print(lives)

#Naming rules (and the habit that saves your sanity)

Names can't have spaces and can't start with a number. So player coins is illegal, and 2fast is illegal. Everything else — playerCoins, PlayerCoins, player_coins — works.

The style Roblox uses is camelCase: lowercase first letter, capital for each new word. playerCoins, not PlayerCoins.

But the real rule is: name it what it is. The difference between local x = 0 and local enemiesDefeated = 0 is not style. It's whether you can read this script a month from now.

#The counting pattern

coins = coins + 1 is the pattern you'll reach for constantly: read the box, add one, put it back.

local coins = 0

print("Coins: " .. coins)

#Common mistakes

• Forgetting local. Luau will create a global variable instead, which other scripts can see and mess with. Keep everything local until a later lesson tells you otherwise.
• Using local twice on the same box. local coins = 0 declares the box. Later, coins = 5 changes it — no local. Re-declaring with local makes a fresh box, which loses your value.
• Naming the box after what you want it to be, not what it is. A variable named enemy holding the player's health will confuse you forever.

Put the lines in the order they should run: