I know this has been a few years since, but for people who are still trying to do this and are using the WSAD controls and mouse, follow these steps:
1. Add the Solid Behavior to the thing you're trying to stop stuff with (Your border)
2. Add the 8Direction Behavior to your player (I know, I know just wait)
3. Go to your player and in your behavior section (under properties) go to 8Direction and put 0's for Max Speed, Deceleration, and Acceleration
Hope This Works!