Played through the first group contestants. Here's my feedback.
Yesterday's feedback
Stroll through the Mole Hill
Great consistent stage involving moles. Starts near the ground and makes the user climb the stage up and down. Mushroom straight from the bat and a mole that can't hurt you if you stand still. For experts there are secrets you earn with walljumps, although reaching the warp pipe is a bit hard.
No pitfalls is also very nice. I would like it if you had a few secrets easy to obtain, because it's an amazing stage.
Spring Up!
I hate to work for power ups, but otherwise a fun stage. Could do without the third pitfall. Liking the trampoline themed stage with it seems a bit boring. A few extra secrets would have been nice and maybe a bit more decoration.
Welcome to Retroland 1-1
The giant mushroom is so good, but it also wrecks your stage. It definitely has the fun factor a 1-1 level should have.
New Super Mario World 1-1
The overworld is great, but that giant pitfall in the sublevel is wrecking. The clown koopa tutorial was a nice touch to it

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Tree of Beginnings
It is not suited as a 1-1 level. I died like 5 times in it lol. The direction is very unclear and there are a couple of brutal enemies in it. Spiked tops on 1 tile blocks, wow. Definitely a shame, because it's an awesome stage. Downloaded it to look at the last secret, dat semi-blind jump!!
Koopa Plateau 1
I really liked the power ups. Buzzer shell on a koopa with a fire flower and a star nice! Gonna retry this one again for more critique.
SMB3 1-1 Redux
Liked the simplicity of this one while still getting the SMB3 feel down. A bit on the short side. SMB3 levels were short, but not that short. Fun little secret. Maybe give the player more space to fly.
Koopa Hill 1-1
Probably the best of the SMW stages. The koopas may be a bit hard on new players, but you're using the pitfalls to get rid of the shells. Kicking the koopas to gain acces to a warp pipe is very smart. I think you could give the player a bit more space to work with. Fine piece of work.
Kuribo's Shoe 1-1
A really cool level concept, but it fails as a 1-1 stage. If you lose the kuribo shoe in the beginning it's over. I like the idea of the narrow space so the goomba jumps up the blocks and you kill him.
Brutal pitfalls. Thwomps and saws are dangerous. The tanuki suit is useless with that last thwomp. And as you know one warp pipe has no exit. I got killed a few times playing this stage. Very neat level tho.
1-1 Difficulty: ★☆☆☆☆
Feels a bit short with a lot of enemies. I like the pipe design with the blocks in the middle. It has a nice SMB3 feeling to it, but not sure if it's 1-1 material. I'll give it another go.
World 1.3 - 1.3
Weird to see SMB in a SMB3 stage hehe. Had to check the door in the editor, nice. Perhaps a bit short, but good enough for a replay.
Super Mario Nexus 1-1
Awful as a 1-1 stage, otherwise a fun level. The first pitfall, enemy placements and all the stuff going on in the screen

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