edits to design.md
edits to design.md

jeremydanielfox/game_engine,brandonnchoii/VOOGASalad,brandonnchoii/VOOGASalad,Jgilhuly/VoogaSalad,PinPinx/TD_Game_Engine,Jgilhuly/VoogaSalad,keikumata/CS308_Tower_Defense,ninasun/game_engine,keikumata/CS308_Tower_Defense,ninasun/game_engine,PinPinx/TD_Game_Engine,jeremydanielfox/game_engine