easiest way to do this?

[xTravax]

hello, what would be easiest way to change value from e.g 0 to 20 (like goes up 0,1,2,3 to 20) and when it reaches 20 it goes to 0 like (20,19,28 to 0) and then starts doing this again over and over again(like a loop)

thanks in advance

[Gr0x]

I made an example with the onClientRender event.

There might be an easier way to do this, but this is what came into my mind.

Untested.

value = 0 
des = false 
function onRender() 
    value = value + (des and -1 or 1) 
    if value >= 20 or value <= 0 then 
        des = not des 
    end 
end 
addEventHandler("onClientRender",root,onRender)