"Bug!" is a 3D platform game which revolves around the player safely progressing through various levels. The game is set on "Bug Island" and consists of six worlds made up of three levels each, with each last level culminating in a mandatory boss fight. Enemies come in the form of insects, mollusks, reptiles, amphibians, and arachnids. Enemies are defeated by jumping on them, as well as utilizing power-ups which include damage dealing spittle and electrical strikes. Each level ends when the player jumps on a "Bug Stop", which will then make the player proceed to the next level. Every level contains collectable items: 1-UPs supply the player with an extra life, collecting a heart will restore one hit point to the player whereas Bug Juice will fully replenish it, and a coin will allow the player to take part in a bonus round whereby they are given the chance to win more lives. If the player runs out of Bug Juice, they lose a life. The game will end once the player runs out of continues.