yah how do you make it so that an object can't go outside of a room (but it should on the bottom and top- this is a platformer that im working on). Oh, and how does the game recognize whether youve fallen off the bottom part of the screen or just jumped past the top?

umm..

Just make a wall object and line the Left and Right with them. Make them Invisible.

In the step event of the character, make a code block.

Code
if x<0 x=0
if x>room_width x=room_width