How do I make buildings solid?

I'm making a racing game and I can get the car to move but, it can go through buildings. I want my car to come to a complete stop or to repel once it touches the building. Please help ASAP I'm in class.

I only kno the basics. plz help

You can not make buildings solid. In Alice you have to code for collision detection. Search the forum for collision detection .

Unfortunately you will find that Alice is very weak when it comes to supporting collision detection.

You can use spheres instead of buildings because you can find the radius easily in spheres. I have a ball game using all spheres to make the collision.

Hey thx. I decided to make a new game for flying jets,but I only know how to make the object move at a constant speed. I want to be able to hold a button and accelerate till I let go of the button. and at the speed i was at when i let go of the button is the constant speed till i change it. I think this jet game will be real sucessful. i'll send it to u so you can c how far i got.
and so youd know im on during school hours for my graphic designing class 2:00pm-3:35pm Mon-Fri(obviously )