The title explains it all, but if you want more detail, like pong. When the ball hits one of the paddles, the ball will flip. Does anyone know how I can do this in Roblox?
You can check their positions, a touched event for GUIs doesn't exist.
What you need is 2D collision detection (SAT) which Roblox doesn't provide but luckily for you it's so easy to understand and implement.
Try finding your own sources but here are two for now: https://learnopengl.com/In-Practice/2D-Game/Collisions/Collision-detection
And of course, our fav developer (or at least mine lol): www.youtube.com/watch?v=IELWpIGtjRg
Hope this helped and good luck :D