In Block Blocks, you draw lines to do what the title says. In the tradition of classic puzzle games, Block Blocks starts with a simple game mechanic and keeps it interesting over the course of nearly countless variations and iterations (actually, 100 levels and 5 endless modes). I think the line-drawing mechanic has never been used in quite this way before, and in the hands of developer Scott Washington, it is the basis for an utterly compelling and elegantly designed puzzle game.

Inspired by the tower defense genre, Block Blocks is a game about keeping creeps from getting by your defenses. In this case, the creeps are squares of different speeds and varying behaviors. Most will just plow ahead, but some will do things like change course when they hit one of your lines. They come in waves and from all directions, and the most effective lines are those that are placed to defend against multiple angles of attack.

Your mouse or finger-drawn lines are not invincible, and the blocks will smash through them after enough hits. A meter at the bottom of the screen shows how much "line juice" you have left; it decrease when you draw lines and increases when your lines are destroyed and when you destroy a block. In a pinch, you can click the grenade icon at the top of the screen to disintegrate all of your lines and refill your meter.

If you let a block leave the screen, it will loop around and come back angrier and faster, and it'll damage your health if you let it get by again.

The game is greatly enhanced by the eerie music, which is generated on the fly based on your actions.

You can play Block Blocks for free in your browser on Game Jolt or Kongregate, and you can buy the Android version for $1.99.