Spoiler: Tube has 10 different labyrinths, each one with a different color.
When you get to level 11 they just start over, with more difficult monsters.
After every third level you complete, you will get to see an "interlude"
sequence. It's basically just a bit of animation thrown in to keep people
thirsting for more. Not to completely ruin the surprise, I won't tell you
how many different interludes there are.
While I was building the game it was important that I (and especially the test
team) could start at any given level. For that purpose I put in the same cheat
keys as in my first Warp
game. Pressing SHIFT and B through J during the
introduction sends you straight to level 2 through 10. That option has been
removed in the official version of the game, but I kept it in my own
copy to let people check out all the maze designs without having to
play for weeks like maniacs (but don't let this stop you from doing that
Off to a bad start? You can reset the game at pretty much any time by
pressing R. Also, you may find the pause function useful. To halt
the game, press P. Do it again to resume playing.