Storyline: 6/10 Fair. You did a fair job of making it apparent for anyone who plays Cave Story what it continues off of. Three points taken off for your poor execution of it, and one point taken off because the cutscene in Cave Story with the island falling shows Curly still dead, so this contradicts Cave Story.
Dialog: 4/10 Bad. "Ohhhh, shiny!" doesn't seem much like Curly.
Gameplay: 3/10 Poor. The falling blocks at the beginning were not good, and only starting me out with one HP, then tossing me to the outer wall where I'll die if I only get hit by one thing?
Custom Music: 3/10 Poor. You only used one instrument track in that whole title screen music. Minimal effort was put into it.
Glitches:
1) At the title screen, I hear a constant text sound. You must've called the wrong event.
2) At the title screen, it waits for me to press fire or jump before going to the main menu.
3) The left edge of the map for the title screen is clearly visible.
4) Blocks begin falling immediately as I start. Why is this bad? Because you can get killed by a falling block before you get the chance to move. This has happened to me several times.
5) The falling blocks' sprites need to be repositioned so that it looks natural.
6) If I die in the core, it fades out keeping the die music going, fades into my start position, back out, THEN back in.
7) When the outer wll loads, I hear the text sound.
8) When I get the sparkler, it fades out then back in.
9) When I go to the storehouse, the room never shows my character, EDIT: Ah, snuck v 0.0.1.2 in while I wasn't looking. The "Uwah!" from Itoh plays when I enter the storehouse. Nothing happens when I go up to either of the doors. It would be good for you to at least have a "You'er stuck." message for them. and I'm stuck.
Improvements:
1) Fix all of the glitches mentioned above.
2) Reposition bits of prtalmond.bmp so that the falling blocks will look right, if you choose to keep them.
3) Use the <PRI command at the beginning of your script for the hor/vert trigger to get from the core to the outer wall.
4) Improve the level design of the tunnel leading from the interior of the outer wall to the outer wall. All you did was erase the solid tiles to make a path for you, which is lazy level design.
5) I suppose that basically the demo has ended once you get to the outer wall? It would be good to make some ingame indication that it's the end of the demo, like make it fade out and display a, "That's as far as it goes for now!" message when you open a certain door. EDIT: Snuck version 0.0.1.2 in when I wasn't looking. Good, glad you added such a room.
6) That empty tile in the storehouse is not too well-executed. When I jump in, I have to the ngo to the side to enter the next room.