How does this game work? (Classic Sonic Simulator)

Hello!
I have been trying to make a game like the one seen here: Classic Sonic Simulator V12 - Roblox (Classic Sonic Simulator) but I can’t seem to do the collision detection and physics like they did in that game. Can you help me? I would appreciate it. Thanks!

(Please notify me if this is in the wrong directory. Thanks.)

im not too big in scripting, but i think (judging by some leaks) its using roblox’s built in physics just modifing them