By now I think everyone on the Internet has played at least one of the five million tower defense Flash games that are out there. (If you're really unsure what that is, see here for an example.) The problem is that they get pretty old after a while; placing and upgrading turrets isn't as exciting after the 500th one. Because it's all mostly static you can fall into a routine, and each new playthrough can be run exactly like the one before. What this weird little microgenre needs is a kick in the pants. It needs freshness. It needs dynamism. It needs physics and giant explosions.

Momentum Missile Mayhem features most of the conventions of other tower defense games -- you're defending against waves of enemies that want to travel to the other side of the screen, undoubtedly for nefarious purposes, and you must shoot them down. You have a certain number of lives, and each time an enemy passes the border, you lose one. The waves get stronger as you go along, and to compensate, you can earn skill points for weapon upgrades.

The very important difference is that rather than laying turrets down and watching them fight, you personally control the single turret on the map. And rather than simply shoot at enemies (so passé), your installation is equipped with a "gravity launcher" with which you fire balls of energy like a slingshot: you grab the ball, pull it back, aim, and let it go. The ball will hit enemy tanks and cause some damage, but will also knock them back and (if you planned it right) into a wall or other tanks. This soon becomes a necessity as you don't have enough energy or time to directly shoot each tank yourself; thus the strategy focuses more on plotting shots to send tanks careening into each other, causing domino effects that lead to mass destruction.

This twist adds about a dozen different improvements to the gametype. One, obviously, it's more exciting to actually fire at enemies yourself than to watch automated turrets plinking away at sheep or bugs or whatever. But it also adds strategy beyond choosing what kind of gun to buy. Pulling the "slingshot" back farther adds velocity but reduces stability, and an unstable shot has a risk (shown as a percentage at the bottom of the screen) of blowing up the second you fire it. Newer weapons are also less stable and cost more energy to use, but have added effects like higher damage or rebounding in random directions. So even while stability and energy reserves can be upgraded through skill points, one must still constantly maintain a balance of what to use when, like whether it's better to fire three quick basic shots that cost 250 energy points each or one slower high-end weapon that costs 800 but could clear out the map if you use it right.

But to hell with all this thinking nonsense, the real fun of the game is just the visceral thrill of throwing big things into other things and making them blow up. One of the special abilities you can buy with skill points is a zero point energy manipulator, and grabbing a tank that's just about to cross your border with ZPE like the hand of God and chucking it into a crowd of tanks to make the whole group explode so hard your monitor rumbles off the table is one of life's simple pleasures. Special abilities, along with some of your more powerful weapons, have cool down periods after use, so you can never come to rely too much on one type. But they sure are helpful in a pinch.

You can play Momentum Missile Mayhem here. It's all Flash, all free, and includes a handy downloadable version. Given the amount of stuff going on, it's a bit more taxing on system requirements than most Flash games, but there are three different quality settings if you find your box lagging.