Bullfrog is a top-down shooter game where you control a frog that hops around and uses its tongue to eat insects. It's a race against the clock to clear the screen of a broad variety of insects, each kind with its own behavior and attributes. Bonus butterflies and bees, flighty dragonflies and horseflies, time-depleting mosquitos, and the ever-present gnat are introduced in the first five levels; after that it's a "Dinner Time" free-for-all with ever-increasing quantities of bugs each level.
The frog's tongue effectively functions as a short-range laser which eliminates everything in front of it. What's really the main limitation is the frog's movement. It's strictly keyboard-based, and the combination of the frog's rather sluggish speed of rotation and ability to only move in jumps. These challenges are welcome, because even with them the game is rather dull. There's a built-in high score and the world #1 (of hundreds of thousands) played for less than half an hour. This may be saying something about the difficulty at higher levels, but I think it's more revealing of the lack of novelty the game introduces past level 6.
Still, it's a perfectly valid time-waster, and the ability to compare your rank on the all-time high scores list in-game is a big plus.