The full PS3 nut is here. This is for the PSP version that is slightly different and developed mostly by a different studio. The main idea is basically the same as players control Sackboy in a cute little ethereal world made up of the unused ideas of humans or something from the opening animation with a wonderful narration by Stephen Fry. Sackboy can traverse the multiple levels with themes ranging from Australian outback and oriental China to ancient Persia and modern Hollywood with fun little physics based puzzles on multiple 3D planes. However, the PSP version necessitated some trimming so there is now only 2 planes to switch between rather than the original 3 and no multiplayer.
The physics are generally fun if a little wonky, but most troubling is when it affects jumping. Just a simple jump, which is about 90% of gameplay given that this is a platformer, is often unreliable and unresponsive. This can make or break the game whether it decides to be floaty cartoon magic or a frustrating slog as you continuously murder Sackboy on electric panels and fire pits because the jump decided you were a little off or worse made you switch planes unwillingly because reasons. This can taint the whole experience, but when it is working perfectly it is still quite a joy with very interesting puzzles with levers, jetpacks, sleds, etc. and a wonderful aesthetic and soundtrack.
The story is barely there both in length and as a motivation for Sackboy to traverse the levels with the only real incentive being the puzzles and the various costumes and stickers to collect. Too bad the small PSP screen makes it very hard to discern what the costume pieces look like, unless they are particularly over-the-top. I ended up with a dino costume and pretty much stuck with that the whole time. The stickers I actually never used outside of what the story required and there was no detriment, so take that for what it's worth. The multiplayer is gone, but the level designer and DLC is still there, but there was a limited selection so many years later and on a less than super popular console.
Overall, not as good as it's full PS3 version, but you might stay for the whimsy and soundtrack. What story that is there is actually different too if that matters to you.
Available on UMD and PSN.
2½ At least the shared energy bar won't ruin any friendships now out of 5