Scratch

I know this is a "repost", but some people may want to use an EXTREMELY simple to use/set up collision script, without changing any aspects of their game.

http://scratch.mit.edu/projects/67589jun/736900

This script can be used in any game where you want a sprite not to go through an object.

Basically, it records where the X and Y of where a sprite is in a variable. Once the sprite touches the color of your choosing, it stops recording where your sprite was and sends it back to the last recorded position of when it wasn't touching the object. This makes it EXTREMELY easy to do what a large amount of scripts can do.

I got the idea from a user who made a project and said in the description that he used the old "Return to last position trick."  I was in the middle of class when I thought of this. Using JUST ONE SCRIPT, I can make sprites with collision to objects.

How to use: Replace the two color blocks with the color you want it to collide with, (Use the "AND" block to add more colors.) set the sensor blocks to the sprite the script is in, and WHAMMO! You are finished.