Defender: A Cool Tower Defense Game
Check out this game: Defender Y3K.
It's a tower defense. Basically, you have a pathway to defend, and enemies, "creeps," are trying to travel that pathway and penetrate your base. You build towers along the path, to destroy the creeps. The towers have different capabilities: range, firepower, cost. You get points (usually shown as $) for every creep you kill, and can buy additional towers and upgrades on the towers you possess.
Sounds very simple, but what it really is, is high addictive.
There's nothing about this game that I don't like. It's got constant action, colorful graphics, and not too many bells or whistles. Those colorful graphics are simple line drawings, making the game fairly easy to follow; you're eye won't get confused by a flood of moving shapes.
At the top bar of the game's flash player, you'll find two buttons: one sends the next wave of creeps before the wave clock runs down, and the other pauses the game. In pause mode, you can adjust the brightness and volume of the game, which is a very useful feature at work.
In the bottom right corner, you'll find the various towers you can buy. Clicking one will show its cost. Clicking a tower you already have will show you its level (towers can reach level 5) and the cost of an upgrade. You can see your score, displayed as dollars, in the upper right corner.
All in all, a fun little game. Try it out.