I absolutely love this concept and this game is super charming, so be forewarned that this is going to be a long post but know that everything I say is meant to be constructive. I feel like this concept is exactly the kind of thing that Mark was hoping for when he picked the theme. The game is just so incredibly charming, and totally reminds me of something that I would've played on the Amiga as a kid. The art style and sound are perfect, and feel like they literally could've been part of a full game from that era. The amount of content is amazing. I didn't get past the level with the cannons, but it would still be a crazy amount of content for a jam if that was the last level.
Gushing out of the way, I feel like the controls are a little bit difficult and make the game kind of a chore at times. They're perfectly serviceable when not much is going on, but as soon as there are a handful of hazards on the screen, I started feeling like I could've predict how Blubs was going to handle.
Another issue I had was the collision. It feels super easy to get hung up on things. I also felt like I died numerous times when I clearly was not touching a hazard. A lot of this came in conjunction with changing sizes, and I understand that can be kind of difficult to rapidly change the collision and convey it to the player in a way that allows them to react. Perhaps maybe a little leeway on the collision and also increase the collision when you puff up on a little bit of a delay would be nice.
The mine enemies not coming back when you respawn makes them feel kind of pointless. I essentially ended up dying to them almost every time and just having to platform back to that spot. I didn't really learn much each time, I just got back to the same spot and continued on.
Only other gripe is that there's a glitch where you land on a surface after being on a wet surface and keep sliding.
But seriously, great game that just needs a little bit of polish. I would totally buy a longer, polished version of this game, so I hope you folks keep working on it.