I had to restart the game several times because of softlocks, and eventually gave up because of this. The first is a pit in the central area (just after the starting area with the gun/dash) that drops you below the screen instead of killing you. The other is when you die after getting the grapple, but before getting the teleport. You get sent back to the central checkpoint, but now you're locked out of the area with the teleport. This is fine for most of the game, but as far as I can tell you need the teleport to leave the area down below after getting the key (the collapsing platforms respawn too quickly to super jump out).

That aside, this is a fantastic game! The art style manages to be super goofy and charming despite the low resolution. All the areas felt distinct and it was generally easy finding my way around. The music and sound effects are enjoyable too. I like the variety up upgrades on offer. The grapple was a bit tricky, but the rest were all really fun to use. My one complaint (softlocks aside) is not knowing which pits are deadly and which lead to other areas. Other than that I really enjoyed the game 

Good game. I like the low resolution style.
The only problems I can point now is the the deadly pit that are hard to recognize