This game is beyond awesome. Though, I wish the demo would've included an item or two.
Hm... how would you like to rom hack the demo?
That's what the site is called. I DID leave the item pickup code in there. Here's a quick thing you can do to change the item you obtain at the beginning:
Using a hex editor, scroll down to offset 15A10 and you should see 69,12. This is the coordinate display item that is found at the start. If you want to see the other items, change the "12" to one of the following:
00 - Key #1 (note: Accessing blocked off rooms will most likely glitch the game out)
02 - Key #2 (The other keys don't have any use for what's seen in the demo...)
04 - Key #3
06 - Key #4
08 - Feather fall
0A - Double jump
0C - High jump
0E - Infinite O2 (There's no water, so this won't do much for you)
10 - Super bullets (acts as double damage; This is going to be renamed "Damage Amp")
12 - Coordinate display
Any other values will likely glitch out. Have fun.