Really fun submission, congratulations! :D
I like the core gameplay: it's simple - but not trivial - and opened to many strategies. I loved to position the little crab to build pillars of barrels, and then try to climb that: it's satisfying! I also appreciated that the player has control over the barrels falling down, and thus the resulting situation - bad or good - it's all player's fault. That's good game design :)
With that in mind, the spikes felt... Unnecessary and frustrating :( They bring chaos, which helps the replayability, but most of the time they just ruin player's strategy. Plus, if I intended correctly the game mechanics, spikes can only be destroyed by a barrel, but to place a barrel you need to be under the same column, but you cannot stay on columns where there are spikes! They kinda break the game, from what I perceived, turning it into a wait for the whole scene to be covered in spikes. Maybe, by making them temporary and/or more deterministic, you could balance the mechanics :)
That is - of course - just my opinion, and I hope this comment turns out to be constructive. In general, I really enjoyed the game, and I'm pretty proud of my second place on the leaderboard :P
Great job, congrats!