hover your mouse over the bar at the top and use the arrow keys or WASD to move. Click squares to select them, and then click the stage to put down that square. To switch blocks, hover over the trash can then click a new square. black is ground, red is bad, and yellow is trampoline. PORTALZ: I have played portal and portal 2, and decided to add portals to a scratch project. Blue portal is entrance and you come out on the last orange portal placed. Yes, you do keep momentum while going through portals and Yes, you can do the "infinite skydiving" trick.