This is definitely pretty good so far, Ruberjig. I still have a few issues with it, as I've forgotten to mention before...
Oohhh, NO. Not this fucking bastard (The Fishin' Boo). He's placed too low, too, resulting in many bullshit hits. I'd raise him by a tile or so, or just get rid of him.
This is likely a minor problem, but if you spin jump trying to get through this hole, you will die.
Ugh, this segment of this horror part is REALLY hard to not get hit. That Porcupuffer resprite and the Grinders and Boo are a bad combo. I'd remove a couple sprites or so.
The GAME OVER text seems a little too close to the right side of the screen. Minor nitpick, though. See below for the odd-looking thing in the status bar.
yay more glitched graphics (the sprite graphics slots 1 and 2 are really glitched up for some odd reason, making the Mushroom and cloud puffs look glitchy...), plus odd looking palettes (the white on the status bar disappears and reappears too, and it's also odd how that Glitchy Mushroom in the reserved slot can still be visible with the white color.)
-No screenshot, but I still don't like how you hid that one P-Switch Yoshi Coin. You should make it more obvious that you should leave the P-Switch there, or just replace it with something else.
-Also no screenshot, but that Baby Yoshi has nothing to eat because you switched the powerup, rendering that Yoshi Coin impossible to get. Did you forget about that, or is there something I'm missing?
-That upside down platform in the second normal section with a coin on it could mislead people to jumping down to their death, even if it is upside down.
-Did you intend to turn those blocked off pitfalls in the first horror-path room into actual pitfalls? Cause they don't seem to kill you. Remember that you won't actually die from falling into a bottomless pit if there is still loaded objects below the screen and above what I'd call the "death line", where Mario dies in a pit if he falls into.
-Someone on IRC mentioned the falling platforms & Boo Buddies are really annoying. I agree. In fact, EVERY single Boo Buddy forces you to wait. I'd either just get rid of them or make them go the other direction, if possible.
Overall, it's still got loads of problems you need to work on, but you can fix them; Don't sweat it.
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