The game gets rather boring after the first level, especially on the last one where it's like 90% flat without any enemies. Perceived through though.
(here was supposed to be a screenshot of the "you win" screen but looks like I accidentally only screencapped to the clipboard instead of file and lost it while writing this)
The upgrade system was kind of meh. The first one was mandatory if you wanted anything else but I didn't even purchase anything other than the health regeneration to reach the end. That already was way too powerful by itself. It would have been nice to have a bigger variety of things to buy and with more frequency to keep up the interest. Now it was very grindy.
And there was no reason to go past the first 10 or so coins while grinding, as past that, it slowed down so much that it would be faster to die and grab the first 10 again. Rinse and repeat until you can buy the upgrades you want and/or need to get through the first level. The next levels do not offer any challenge whatsoever, other than maybe falling asleep.
The first level, though the best and most interesting of the three, was a bit annoyingly designed. The top route has some very annoying jumps (especially that first downslope gap) where getting past with the inconsistent jump height/distance did not feel great. The lower route was a bit more guaranteed to progress, but the enemy spam made it so like 50% of the coins could not be gathered. And the randomish mega bounce so you hit your head on the top platforms was a bit unfair. And then finally had that choke point that I'm pretty sure is impossible to get through without the armor upgrade at least. I made it through by first going a bit on the top layer until I failed some jump and lucked through the hole without getting stuck or completely getting bodied. Proceeded to run on the bottom until I somehow made a lucky mega jump back to the top and continued there until the routes merged back to one. From that point on, the game posed no threat at all.
I'm all for the goofy aesthetic and overall feel of the game, but it still could use some polish around the edges. Like the completely broken ground tiling was just off-putting. I really prefer the actually repeating one you have in that main picture. I like that character model more too. The running speed and animation felt not properly synced. Could have controlled the animation speed a bit more based on the running speed so it'd look more natural, just like you stop it when jumping.
I liked the background with the parallax effect. Could have toned the vertical parallaxing a bit though; it felt a bit much. And obviously, it didn't really fit that well with the rest of the visuals. Pixel size wasn't consistent either, and it was too blurry.
I was very annoyed about the control scheme. Having to click retry with mouse while game itself was keyboard only was bad. And arrow keys as an alternative to WASD would always be welcome, especially if the game doesn't use mouse at all. But I did discover that you can jump with mouse too which made it that much better.
Could have used some love in the sound department too. Loved the cheesy classic tunes, they fit the game feel perfectly. Would have liked to hear a bit more sound effect though. I think there was only jump and coin sounds overall. Adding sound effects for footsteps (something quite slight), getting hurt and monsters themselves could have made some noice too to fill up the void.
But yeah, all in all good job with the game! 👍