Let me give you a hand: I'll review this by stating the most important points that stand out to me. I know it's an year old.
– As others have hinted, it starts out dubious as it's not made very clear that there is no additional control or mechanic other than moving with the movement keys. Clarify it in the description? Saying that "They will step on you to get higher" didn't quite make it. Maybe "Think carefully: move and carry them whatever way you can" instead would be better. It's confusing (and a fail) to have hands in a game where you can't grab or hold. The identity that speaks along should joke about this.
– Without being too detailed, the order of the levels just seems screwed up. After the initial harder ones came some very easy levels that I beat right away. (It could have been due to learning how to play.) This is disappointing later on and discourages people from sticking to the game at the start.
– Pushing stuff isn't very consistent. You should have sorted out how pushing works under all scenarios as well as the overlapping bugs that there are. Removing a hand from under an object and sliding another object underneath it with the other hand right after is possible with some objects but not with others, which doesn't make sense. It also causes overlapping bugs that someone already mentioned. With a hard game that's supposed to have players looking for obscure ways to beat it, you should have sorted out all the possible interactions. Plus, it's a simple game so making sure that it's working consistently and without bugs isn't much work or asking much.
– I couldn't tell when the arms were stretched to their maximum and it harmed the gameplay.
– The level selection is interestingly nice but the navigation is broken. In a game I always want to be able to return to the main screen at all times. On the ending screen, there are no navigation arrows and it's impossible to exit. I have to restart the whole game to get out of the end screen. Terrible. The mouse cursor doesn't turn into a hand when hovering links, breaking a standard and creating a clickbait-like ending. I didn't mean to open your website, I just wanted to exit the end screen and check out some other levels again. Plus, the levels aren't numbered. I can't refer to them or know how many I beat or how many there were without counting – bad.
– Despite probable strong opposition to this view, the graphics choice is awful. Retro is cheap, overdone and looks horrible. This particular puzzle doesn't really justify it's use. It would look much better with a certain sleek modern artwork that I can only imagine myself. It's not the cartoon type.
– You should use the Newgrounds advertisements API in-game so you could profit from it. Also, developers can't excuse any poor quality in their games by saying that they aren't paid to make them when there's an API.
– A level creator (as in the game Tentacle Wars) would allow everyone to find more quality levels, as they would be up-voted. But I don't really mind too much that there isn't one. Although on the other hand, Sokoban games almost always have level creators.
– It's an epic premise playing with the two expandable arms.
– This original genre derived from Sokoban is awesome. Maybe it hasn't even been done. It's really great. It's a whole new game.
– The level design is good. So many games with bad level design, but not this time. Also, as someone else already said, it's challenging without having brute force difficulty like a pixel hunt, button smashing or a giant layout. This is further seen in how the arms' length was kept the same throughout the game. If it were someone else with the typical brute force difficulty, they would just make a big level with very long arms. But not this clever author. Good work. It felt so nice figuring out the first levels! The logic was just so sweet, really good.
– All games should have secrets and bonus things. There appears to be only a little one here that may have been unintentional, but that I still like very much. Throughout the game an identity antagonizes the player. In the final level, the walls resemble spelling out "FU," an initialism that ends up meaning "screw you." It's not explicit though. Subtility is very witty. It's boosted by the ending screen right after having "END" spelled out with the walls, establishing the context of writing with them.
– The game has several other nice touches in addition to that one. It turns black and white after loosing. It displays the word "reset" briefly when resetting. Far better than the popular hideous transitions that other games came to have. I wish, however, that the word "reset" would appear for as long as the R key was held. It's downloadable! Thank you very much for caring about that. Host the download at Dumping Grounds so that when your website dies it's still available on Newgrounds. It starts playing on the actual main screen! It has that nice take on the arms' movement sound. It has no introductions or fake preloaders starting right away. It has the improper entries, like Play and Forward, of the right click context menu removed, but leaving the useful ones, Quality and Zoom. Only the naive disable everything and put an advert in their place. Don't forget you can build Mute into it, the right click menu. These are all good things. We have a witty game designer here. The author of this game should definitely check out the game "You Have 8 Bricks" (ID 654221) to find similar creative and professional game design elements.