yeah some of the tubes are a little to transparent.. perhaps adding a fade to them (^_^)
generally it was playeably fast, but in some areas i wouldn't want to have to be running from ghosties
would say it ranged from 25-60+ fps some areas and like the longer looking areas i'd be quite slow - perhaps you could add an "if object screen x() > 0 and object screen x() < screen width() etc... etc..."
and then hide everything offscreen
and that texture for the box looks like its been scaled a few times too many (^_^), remember the more times you scale a texture to an object the greater the rendering and tex memory.
this was on a
Duron Mobile 600Mhz
128Mb Ram
GeForce2 Go! 32Mb
DirectX 8.1/9.0
Win XP Pro SP1

the music reminded me of a creepy Doom level hehee
Tsu'va Oni Ni Jyuuko Fiori Sei Tau!
One block follows the suit ... the whole suit of blocks is the path ... what have you found?