You have a nice song choice that's very fitting with the graphics you used. In general you create a nice jovial environment for the area. Watch some of your bgo placement. You don't want trees with the falling blocks otherwise you create some more cutoff. I didn't progress too far into the level when I already received a 1up from 100 coins. Having coins is fine of course, but you don't want every block to contain 10+ of them. I went and checked the coin total and you have 1006 coins in the level. You definitely want to lower this significantly maybe to 200-400 if you can. You have a bad case of npc spam in the level too. You have a section with way too many goombas and a couple small sections with koopas and goombas cluttered together. You need to space out your npc's even if you want to use a lot, so I'd be more considerate of the space you create and how many enemies and coins you should truly have in there. It's pretty odd that you have two checkpoints as well when only one of them will actually work. I understand that both branch out into two paths, but it's still weird. The level itself is also way too short so there's no use to having checkpoints at all honestly. Another thing to point out is that you should get rid of the invisible blocks when you exit one of the pipes that's right of the outside checkpoint; instead you should put some visible hill blocks in there that prevent the player from passing through, it'll be more aesthetically pleasing. The actual game play was bland with its npc spam and pretty confusing paths. I know I generally like to be able to explore levels, but when I see an alternate route and can't go through it becomes really annoying as what you did with the invisible blocks. On the bright side it was clever to have the player backtrack through the cave to get the secret exit with the key you find towards the very end of the level. In that same section though you have some platforms that didn't show up for some reason, so that's something else to look over. Overall the level looks nice, but the excessive npcs, minimal length, and poor gameplay bring this level down immensely. I hope you can work through this again.
2.7/10 Moved to the Trash Can
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Pretty much everything I have to say about this level was said by The Thwomp King.
While I can appreciate levels that stay mostly linear, but have side paths (Super Mario World comes to mind), I just find it hard to appreciate the side paths when they're thrown right in your face and not really a "side". The level is also extremely easy to beat, even for all of the enemy spam.
My first complaint is that there are enemies that appear right after you exit pipes, and the problem with this is that, while you might know where the enemies are as the creator, your players aren't going to know that there are enemies on the other side of the pipe, and this can lead to some quick death or power-up loss. Speaking of power-ups, I only found three throughout the entire level. Typically, I would set a ratio of power-ups in your level. 1 power-up for every 10 enemies, or at least in a World 1 setting, I would increase this by 5 for every world after the first, so 1 power-up for every 15 enemies in World 2, 1 for every 20 in World 3, 1 for every 25 in World 4, and so on.
Another problem I had was in the cave, where the background and the foreground sometimes clashed together and blended with each other, but that's just a minor qualm compared to the rest of the level. Other than that, my review is basically The Thwomp King's review.