The MOUSE_PRESS event runs every time a mouse button is pressed
Takes three number parameters, a "button", which is the number id of the button that was been pressed, the "action", which is the status of the press event (0 for release, 1 for press, 2 for hold), and the "modifier", which is a bitmask number detecting if you have any modifier keys being pressed (like shift or alt, for example)
If returned true, the event cancels its vanilla function