I played this, and it's good hack... well, almost. All levels have the same strategy. Just run'n jump. It makes partically all levels feel samey. There are occasionally gimmicks, but they usually don't have interesting executions.
Aside from slowdowns, there are a lot of other issues.
Why goombas have stomped koopa GFX?
When I kill enemie with fireball and touch it at the same time, Mario's head appears instead of smoke
Why small mario uses standing frame when ducking? It looks weird.
Is that me, or sliding big Mario looks weird?
Strange things happen when you use yoshi. I don't remember if it's only for 6-2
Gulp is glitched too. Help!
I can simply skip 7-1 by grabbing 3-ballons and fly, fly adn fly...
Why I can't firekill Yellow para-koopas?
Nothing too serious, it just a little strange.
Star Roads lead to bonus room. After beating 8-4, starroad lead me to first world, but it doesn't appears in world 1, when you enter it, you're in bonus game. Same for not unlocked starroads. If you enter any star road from world 9 that you didn't unlocked it in normal world,
I can enter it, and BONUS GAME
All 7 first bosses are super easy to defeat. I'm pretty sure bosses should be harder with each world. But they're just meh.
This fire doesn't have interaction? I can just go throught it!
Those chainchomps are hilariously strange. Their GFX just X-flipped, making them look weird.
Why I can't spinjump on those chomps? Not cool.
I can still scroll screen with L and R when eaten by Boss Bass, but for some reason Layer 2 scrolls too. Only works when you eaten.
Statue's palette affected by Mario's. Now it doesn't looks good.
Peach looks weird. At least to me.
Aaaand... that's all I can say. This hack is good "classic" platformer, but it can get repetitive with one and the same level "formula". 7/10