There are 20 Inner Tube levels. Each level starts reddish and most fade from red to orange, yellow, green, blue, and purple as you progress towards the end of the tube. If you reach the end before your time runs out you move on to the next level.
You can go directly to any level at any time by going to File->Jump to Level...
1 - Earth Underground 2 - Earth Station 3 Sky Tube
4 - Space Station Entrance 5 - Space Station Engineering 6 - Space Station Computer
7 - Space Station No Access 8 - Alien Passageway 9 - Alien Tunnel
10 - Alien Zits 11 - Alien Stomach 12 - Alien Exit
13 - Star Passage 14 - Sky World Glass 15 - Sky World Web
16 - Sky World Windows 17 - Sky World Spider Lair 18 - Metal Dungeon Mold
19 - Metal Dungeon Gleam 20 - Metal Dungeon Black
