Hi Megaman
You are right that setting the sync rate to zero would make games runs at crazy speeds, but locking the fps at 30 isn't the best way to do it. If you use the sync rate 0 command to run at full speed on your pc, but don't sync once every loop, but instead sync 30 times a second by using the timer() command, your game will be super smooth and run the sam on all pcs
My current project has the sync rate set at zero, gets 500+fps on my best pc, 50 on my worst. However it runs at the same speed!
The increased fps adds smmothness but the speed of gameplay is the same
To see how I do it, look at my sonic code in the "2d sprite bug rich" thread in 2d
Or IanM and Raven and I'm sure some others have similar ways too
If u want any help with this, u can email me my friend, its really worth doing!