Is it tile based or are you going to draw out your own levels? If you draw out your own you can probably just make a blank wall MC and a floor MC with hit detect code inside that moves the player back. Then resize / overlay the MCs over your level.
As far as angle is concerned you will need to use sin / cos.
so if I wanted to move a bullet at a 45 degree angle with a speed of 20 here is the code.
//must convert the angle to radians for the Math functions to work
bulletSpeed = 20;
angle = 45*(Math.PI / 180);
vX = Math.cos(angle)*bulletSpeed;
vY = Math.sin(angle)*bulletSpeed;
bullet._x += vX;
bullet._y += vY;
This may or may not answer your question...but you weren't too clear.