A true classic of it's time
This version of tron based itself off of the light cycles in the movie. Basically, just like the movie, you move your light cycle trailing a wall of light (in this case a line). You're pitted against the other play (be it computer or human) and whoever ran into the wall, opponent's trail, or own trail, lost the game.
It's a simple game, but surprisingly it has some great multiplayer value and interesting strategy for a "snake-like" game. I think snake on mobile nokia is newer though--so really, snake is a tron-like game.
You also get a boost feature to speed past the computer. There's a few difficulty levels. And even though this game is simple, it's surprisingly addictive and fun.
There's been so many clones on this game and some have been better than others. You can probably find a game similar to this on the net as an online game, freeware game, etc. The best Tron clone I've found, to date, is GLTron. It's freeware, and it was the first 3D tron I've seen. And does a great job as well! You can also hook up a joystick/controller to it, which is nice.
Find this game--it's short and sweet. But you'll be coming back for more.