Jelly Defense is a very nicely designed tower defense game. As in any tower defense game, you have to prevent your enemies from reaching a certain point in the map by placing defense towers strategically. Jelly Defense has great, original graphics. At first sight, the game looks like it belongs inside a microscope. You control the Jelly forces, who are trying to fend off an alien invasion. The aliens are after your diamonds, and you have to prevent them from getting to them if you are to be successful. Each downed alien drops coins, which you can pick up and use to build more defenses. Each tower can be sold and upgraded at a cost. Certain towers target specific enemies, and won't even fire at others. That is why you have to always pay attention to the information dialogs that provide you with this information. Some towers target groups of enemies, so having a good combination of both is the way to go.
Jelly Defense has a great tutorial that quickly explains all the gameplay elements as you play. After that, you are off to play the missions, which become unlocked as you complete new ones.
In short, this is a nice tower defense game, with great gameplay and beautiful graphics.