As written in the N in-game help:
- "It won't stop weapons, but it's kinda fun to jump on."
Bounceblocks are those white blocks hanging around. They won't stop enemies, won't block shots, won't divert anything, but they are solid and you can't walk through them (sadly). They wobble when you touch them, which is where the "bounce" part comes in. For some serious air on these things, the key is to wait until the bounceblock goes all the way down, and when comes back up, jump. You should go fairly high into the air.
Numerous bounceblocks combined with an extremely annoying enemy can cause some frustration in a level. A great example of this is 74-4: Zenith, where there are a whole bunch of bounceblocks and a single homing missile turret.
- 74-4: Zenith
The bounceblock can be used to pull of some useful jumping tricks - in fact, mastering these skills are quite vital in completing and mastering N. One of the most important is the double jump, which you can find here. Another trick is that you can pass through them at high speeds, causing you to slow down.