I have to say that this game is, by far, the BEST out of all the "Tunnel" variants that can be found in the Archives. The main reason is that it's got a ton of customization options, and the graphics are smooth even at dramatically high speeds. It also features four-directional movement, though I can't imagine why you'd want to move up and down.
If it's not obvious, Ultra Tunnel involves a little spaceship (that's you) racing down a twisty tunnel. You just use the arrows to move and stay alive as long as possible. High scores are kept for every possible combination of options, so there can be no real comparing of skills unless the participants both use the exact same customizations; a must in games such as this. You can reset the high score for any given combination with the touch of a button.
"Speed" does what it says on the can. The Slow speed is still pretty fast, though when you set the other options to their easiest, it's a cakewalk. Insane speed is only for use with super-human beings; it's so blazingly fast that your calculator screen may catch fire and you can barely even see the warp-speed walls coming at you until you're already dead. "Difficulty" affects the width of the tunnel, thus making it harder to dodge incoming walls as you don't have much space to maneuver. Lastly, setting the game to "Classic" game play results in almost constant movement as the tunnel curves sharply left and right, while "Random" gives you a much straighter tunnel with a few bends and nasty bits thrown in; good if you've got the other options set in a particularly difficult way. Lastly, in case you're feeling wild and crazy, there's a button for randomizing all three settings.
Fun Level: Sky-High
Addictiveness: Pretty Darn Addictive
Replayability: Good, Better With Friends
Annoyances: None At All
Final Score: One of the few absolutely must-have games out there. Twenty-four dimensions of fun!