Going Down Achievement
You can only get this towards the end of the game. For the first couple of times you go on the falling platform, it will only stop at three levels. But later on, as you get close to Singe's lair, you will encounter the falling platform again. This time it will stop three times to the left, then three to the right, then a final three to the left again. Simply step off on the final platform to the left. It's dead easy to count it. BTW I have encountered this level in mirror mode, so the stopping points are simply reversed to three right, three left and three right again. The achievement unlocks as Dirk climbs to safety.