A kaizo::hard hack by worldpeace from 2014. This hack features many bullethell section. Comments and timestamps below.

Comments
I always love hack that have nice and detailed backgrounds 00:42 They make the levels more atmospheric.
I would have done a reznor glitch at 01:35, but this hack uses SA1 and Bizhawk does not map the SA1 memory, so you can't use a lua script (even ram watch doesn't work). I'm also not sure if the reznor glitch works with SA1.
There are so many creative bullethell section in this hack 01:26 02:33 03:41 15:07 (+ the boss fights)
The section at 02:57 took me a while to figure out.
L+R totally breaks this coin snake section 05:55
The dino rhino didn't spawn at 06:27
I'm glad that I did the break at 06:54 to keep the key, as this skips the balloon auto scroller section.
Bad cape filter is bad 13:19
This bubble jump is by far the hardest part of this hack 13:49
The controllable PBalloon was a cool gimmick and made for some interesting sections 14:20
That's a neat final puzzle for this hack 16:04

Timestamps
00:25 Emergency (level)
00:38 Tubular (level)
04:03 Fruit Dealer fight
09:37 Ordinary Big Boo fights
14:18 Controllable PBalloon section