Pretty good entry for a one person game. First of all it is harder than expected I managed to deliver 2 cargos and I was hafway there in third one(the rising lava part). The amound of content is really good (double jump, ice, lava, chainsaw, maybe things that I couldn't discover). And absolutely magnificent level design. The levels and places of checkpoints are smartly choosen I can say. Also nice little story. And the way game teaches new mechanics is also perfect.
For difficulty issues I guess the hitbox of the spikes should be a bit smaller sometimes I died even though I was on the floor and spike is on the edge. And chains saws could have been a bit smaller. Also levels could be a bit shorter I think not so many people are willing to play it for 10 minits and even though I did I couldn't manage to deliver third cargo.
I loved the game I think it deserves some more development good work.
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Thanks for commenting and taking the time to play through a hole loop :)! Yeah the hitbox of the spikes is a problem, I didn't know how to manually adjust them (they're used in a tilemap) so I went with the default hitbox, which is, as you pointed out, bad on edges. I was also surprised when I watched some other people play it, that the platforming was harder than I thought. Definitely something I take with me, that some jumps that may seem easy for me (as I'm used to how the player jumps, moves etc.) aren't for someone thats playing for the first time. Also shorten the levels is good advice!
Oh, and the thing you missed was a gravity cave where you could change gravity from +1 to -1 with different switches.