Despite its name, Microbe Kombat is no Mortal Kombat, or indeed even Mortal Pongbat. It's clearly a game where the developer came up with an idea, thought it would make a neat game, and then made a game out of it without actually working out the game mechanics so that it was a neat game.
So, in Microbe Kombat, you're a microbe swimming in some kind of broth (you move with the mouse), and enemy microbes are also about. From time to time, protein randomly appears in the broth. If you eat the protein, your size increases, and you also acquire an item, which you can use to give you various temporary boosts (increased speed or size, for instance). Microbes can eat other microbes smaller than themselves, and the goal is to eat all enemies while avoiding being eaten yourself. Eating an enemy is apparently as simple as running over it when you're bigger than it, except that the eating mechanics are extremely fussy and nine times out of ten you'll end up failing to eat the enemy for no discernible reason. Later levels introduce viruses; if infected by a virus, a microbe slowly gets smaller until it lyses and releases more virus particles; winning while infected is difficult, but possible, if you manage to collect a lot of protein. Still, it's almost always a death sentence. The virus can also infect enemy microbes (in which case all you have to do is survive until they perish), although some types of enemies are immune.
The special feature of the game is that one of the items allows you to divide yourself into two microbes, and the enemy also occasionally fissions into two smaller microbes. (One of the action items also allows you to switch which one of your team you're controlling, if you have more than one microbe on your team.) The problem is that this is strategically totally unbalanced -- it's clearly more advantageous for you to have one microbe that can't be eaten than two microbes that can. Indeed, this becomes very obvious very quickly, since most of the strategy consists of waiting for your enemy (who is usually bigger than you, since they usually start out with a size advantage, which makes it easier for them to grab more protein) to divide, and then eating the two halves. This makes for a rather unsatisfying game experience.
The graphics are pretty nice, although the eating animations look kind of strange. (The title screen clearly is influenced by Juno's lettering style -- it's very similar.) There's not much in the way of sound effects; the background music is kind of creepy -- it's kind of a good complement to the game, but also a little weird. The game is not particularly long; there's only 12 levels in all, and although some of them are rather annoying, it shouldn't take you too much time to make it through them all.
Overall, Microbe Kombat is a pretty average game. The concept of being able to divide your microbe sounds really neat at first blush, but it doesn't really work very well in the framework of the game, and the rest of the gameplay just isn't interesting enough to carry the game. As is so often the case, the game seems to compensate for a poor AI (which, in this case, is one which divides when it has the size advantage, thus giving up the size advantage) by giving the AI lots of advantages, which is almost always really annoying. It's not a terrible experience, but it's not a game I really was thrilled to have played, either.