Perhaps a good idea to also gt rid of all includes to collision.h. :)
From now on the menu buttons only react when they are finished moving down/up.
The left and right keyboard keys now work in the Level Selection submenu; the amount of buttons is now stored per menu; using the scrolling wheel on your mouse now works again properly; navigating through the menu with your scrolling wheel only allows to move one by one button from now on; updated TODO.txt; added text files up to level 7 (no proper design yet, just basic ground tiles and a sky);