It's a nice little experience, although I'm surprised that it's quite so acclaimed as it is.
It's a very light puzzle platformer. You play as a series of squares or rectangles, each of which has a different colour, a different size, different jumping heights, and some have bonus abilities like double jumping or floating in water. You traverse levels by switching between characters and stacking them up to use their abilities appropriately to get through the levels. When you get to the end, each square has a box they need to be in to go to the next level. There are 100 levels. The pacing is good, there's always new stuff, levels only take a minute or a minute and a half. None of the levels really have any challenge, it's generally immediately apparent what you have to do and there's only really one mechanic that actually presents any challenge in executing what you need to do (one block type has reverse gravity and you have to sort of lasso a falling block on top of a falling upward block so they sort of meet in the middle and float off each other). Some levels have a single collectible.
It took me apparently 2.9 hours total, but that includes doubling back and getting a few missed collectibles. It's very pretty because it's just made of primitives. The music is really really nice.
I guess the main thing that the game does that's unique is that it has voiceover narration that provides an inner monologue for the blocks, who all have personalities. This is pretty nice, very well written, and cheeky, and it's cool to think of coloured blocks as human-like characters, but ultimately the "plot" is unclear--something about hacking the gibsons to free the information mainframe or whatever--and most of the personalities don't really go anywhere or lead to payoff. One very cool thing is that as the voiceover speaks, there are subtitles that appear next to the character you're playing as... but as you move, the subtitles waterfall so that you always see them on screen... so if you're at the right of the screen you might see the subtitles on one line to the left, but if you run to the left and there's less space, it sort of squishes into five or six lines. It can't really be described, it's like the effect that happens if you resize your browser window horizontally and text wraps, but applied to cool effect.
So all in all, I'd say it's well worth the 3 hours and cute and I'm looking forward to what the dev does next, but it doesn't really stick with me, even now and it's not super substantial. Mild recommendation.