* Toggle sound and/or music at menu and pause screen.
* Show points gotten per kill. A little floating, fading points text would work.
* Mosquito charging sound
* Acid sound
* flies buzzing ambient sound in stomach levels, underneath the music.
* fix movement
* gray out purchased upgrades, or stack upgrades.
* gray out upgrades unable to purchase
* Keep score visible after purchasing upgrade. Should update, too, if it doesn't.