Use your mouse to move the square to see if it is colliding with the other square. When not colliding lines will show up in the middle of the screen, their x coordinates(y is irrelevent due to the way I am drawing those lines) not overlapping shows that the shapes are not colliding.
red lines are normals, click 1 to toggle the visiblility of them This is useful for a game using a lot of clones, each storing its Data in a list, the touching block wouldn't work well if you wanted to know which one you were actually touching. (you could just use distance or x and y in a certain bound, but that wouldn't work for any rotated rectangle hitboxes...)