Pico8 Lua cheatsheet

22 Oct 2017

Two-minute read

Simplified, adapted from Pico8 about txt file

Pico8 Editor

Comments

-- use two hyphens like this to ignore everything until the end of the line
--[[ multi-line
comments ]]

Types and assignment

Types in Lua are numbers, strings, booleans and tables;

NUM = 12/100
S = "THIS IS A STRING"
B = FALSE
T = {1,2,3}

Conditionals

IF NOT B THEN
	PRINT("B IS FALSE")
ELSE
	PRINT("B IS NOT FALSE")
END

-- with ELSE-IF

IF X==0 THEN
	PRINT("X IS 0")
ELSEIF X < 0 THEN
	PRINT("X IS NEGATIVE")
ELSE
	PRINT("IF NONE OF THE ABOVE")
END

IF (4 == 4) THEN PRINT("EQUAL") END IF (4 != 3) THEN PRINT("NOT EQUAL") END -- note that != can also can be written as ~=

LOOPS

starts with 1, NOT 0

FOR X=1,5 DO
	PRINT(X)
END

FOR X=1,10,3 DO PRINT(X) END   -- 1,4,7,10

FUNCTIONS

Y=0
FUNCTION PLUSONE(X)
	LOCAL Y = X+1
	RETURN Y
END
PRINT(PLUSONE(2)) -- 3
PRINT(Y) 	  -- 0

TABLES

In Lua, tables are a collection of key-value pairs where the key and value types can both be mixed. They can be used as arrays by indexing them with integers.

A={} -- create an empty table
A[1] = "BLAH"
A[2] = 42
A["FOO"] = {1,2,3}

-- Arrays use 1-based indexing by default

A = {11,12,13,14}
PRINT(A[2]) -- 12

-- size of a table indexed with sequential 1-based integers

PRINT(#A) -- 4

-- Indexes that are strings can be written using dot notation

PLAYER = {}
PLAYER.X = 2 -- equivalent to PLAYER["X"]
PLAYER.Y = 3

GENERAL PICO8 CARTRIDGE NOTES

To generate a preview image saved with the cart, run the program first and press F7 to grab whatever is on the screen.
The first two lines of the program starting with ‘–’ are also drawn to the cart’s label. e.g.

-- OCEAN DIVER LEGENDS
-- BY LOOPY

Additional PICO8 Commandline notes

folder - open the carts folder in host operating system
ls - same as Bash
run - run from start of program. call inside a program to reset it.
reboot - useful for starting new project
printh str [filename] - print a string to host operating system's console for debugging

Program Structure

_update() - called once per 30fps
_draw() - called once per frame (loops) - normally 30fps
_init() - called once on program startup