hello world - nesbox/TIC-80 GitHub Wiki

The Hello World cartridge is the default cart created by the new command.

t=0
x=96
y=24

function TIC()

	if btn(0) then y=y-1 end
	if btn(1) then y=y+1 end
	if btn(2) then x=x-1 end
	if btn(3) then x=x+1 end

	cls(13)
	spr(1+t%60//30*2,x,y,14,3,0,0,2,2)
	print("HELLO WORLD!",84,84)
	t=t+1
end

The first argument of the spr function corresponds to the sprites indices. The formula 1+t%60//30*2 switches from one sprite to the other to animate the character.

Let's explain it:
The two sprites have indices 1 and 3 so we need something that switches from 1 to 3 regularly.

In lua % is the modulo operator, it returns the remainder of the division.

> eval trace(154 % 60)
34

Because 154 is 2×60+34.
So mechanically t%60 increases with t from 0 to 59 and then restart at 0 when t is a multiple of 60.

// is the floor division, it divides the number, then truncates it.

> eval trace(34//30)
1

So t%60//30 will be 0 when t%60<30 and 1 else.
Therefore 1+t%60//30*2 switches between 1 and 3.

The default Hello World cartridge template can be modified using config default command. That can be used to use a custom palette for all your projects. Do not forget to save.