Hey Katie,
Currently App Lab doesn’t easily support this kind of interaction. There’s no command like turtleIsTounching(color) which a student could use within an if-statement to prevent a turtle from moving through walls, change the score, etc. There are ways you could do this by manually performing collision detection (i.e. keeping track of the locations of all walls and the turtle and comparing to make sure the turtle isn’t touching one), but depending on the programming ability of the student that can be fairly challenging.
Let me know if you need more help guiding this student. Also keep an eye out for Game Lab, the new tool we’re building for the CS Discoveries course. It will have much more built-in support for the types of collision detection and game development you’re looking to do here.
Cheers,
GT