Donkified the background and double donked the explosion.
Added explosion sound effect.
Added Credits state.
Remade gerters to the correct size, so there's no more weird offsets.
Can now pause music by pressing 'P'.
Updated gerter sprites.
Added ledge to Credits, Dead, and Menu states.
Added sfx for when you pass through a gate.
Removed reference to old 'background' image.
Added patch number to menu.
Added jumping sound effect.
Initial mobile support. (very weird physics)
Might have to redonk the jumping system, since it's time based and is
calculated after the update loop.
Updated index page to center the game container.
Added fire barrel towers.
Removed unused field from tower pairs.