You mean that your players levitate?
If yes, you need (for the beginning) simple gravity to keep your players on the ground.
Code:

---

 
function gravity
{
	while(me)
	{
		vec_set(temp, my.x);
		temp.z -=  500;
		trace_mode = IGNORE_ME + IGNORE_PASSABLE + IGNORE_SPRITES; 
		result = trace (my.x, temp);
		my.z -= result;
	wait(1);
	}
}
 

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