// you can use this
if on edge, bounce

// if you are moving in a certain direction you can use
if <touching [edge v]> then
set (direction) to <(180) - (direction)>
end

//If you are moving with X and Y velocities, you can change the sign of the one of the velocities, based on which wall you hit.  See

if <not(touching [sprite1 v]> then
move (5) steps
end

//

if (touching [sprite1 v] then
set (X velocity) to (0)
set (Y veliocity) to (0)
end