The premise of Fragger is very easy: You have a bunch of enemies on the screen, and your job is to throw grenades at them to blow them up or knock them off the screen. This is complicated by destructible partitions and the need to get the grenade throw just right. When you do get it right, however, the result is a heavy explosion with body parts flying over the screen. While the violence is cartoonish, it really has no right being this much fun.
The puzzles aren't just about throwing grenades in the right spot. Sometimes you are expected to throw multiple grenades and have them detonate in a complex sequence to achieve your goals. Sometimes, even those levels work, but there is the occasional difficulty spike, where you may have tried the correct solution, but the timing is so precise that it comes down to luck whether you succeed or not.
The Flash version, and its sequels - Fragger: Bonus Blast[c] and Fragger: Lost City[d] - can be seen as teasers for the Miniclip-developed iOS version. The iOS version contains eleven worlds, ranging from the Flash-version's "Counterstrike"-like one, to outer space, to Atlantis and a special Valentine's Day world. All in all, it is a wonderful little game that is easy to pick up, fun to play, and incredibly addictive.
If you want more, there's also Monster Island, also by Miniclip, with the same premise of throwing explosives at enemies.