Move within boundaries?

Question

If I have a box of 100x100 steps
Top left = (0,0)
Bottom right = (100,100)
Each step = 10
Direction = 0 to 2*PI
When ever some one commands movement
dx = step * sin(Direction)
dy = step * cos(Direction)
if(x>0 && x<100 && y>0 && y<100){
if(forward){
x+=dx;
y+=dy;
}else{
x-=dx;
y-=dy;
}
}
PROBLEM:
Logic works ok for movement as per present direction until hitting boundaries, but then gets stuck at boundaries, any one with some solution?

Here is how I am using it
https://code.sololearn.com/WrXGkNW6aSdl/?ref=app

Answer 1

No, I want it to stop at hitting boundaries, but still able to move away from boundaries.

Answer 2

Do you want to appear on the opposite side of the rectangle ?