Darkness, and running out of space

This weekend's work was to add dark rooms. (at least, dark until you have the lantern) Which has been tough. I've given it a ton of thought, and have never been completely happy with what I've come up with. But with a good bit of trial, error, and wasted code, I've got something that works:

Dark rooms are limited to a single enemy. What I do is a trick that dates back to the catacombs from Adventure: I use an enemy sprite (set to 4x width) in yellow as a glowy area around the player. Then I change the background and walls to the same color, but change the rendering priority flag to put the playfield (walls) on top, the sprites 2nd, then the background last. Which means that everything looks black unless the glowy light is there, which gets rendered underneath the walls, showing where the walls are.

Thank you, Warren Robinett, for this awesome idea.

Now because I have other enemies that I want to render as well, I have to have some flicker going, and render the light and the enemies in alternating frames. (I just don't have the code space to do the more complex alternation if I have more enemies).

The one thing I have left with the darkness is that I want to hide the enemies until they get close to you. Which actually should be pretty easy, i believe.

Now the problem that I'm having is that I'm running drastically low on ROM space. I've got about 1K left of my 16K. In that space, I need to add a bunch of room layouts and color schemes, code for the dynamite, a bunch more enemies, and a sequence for winning the game. I also wanted to add support for the SaveKey, a cool doodad that someone made that plugs into the 2nd player controller port, and allows persistent storage for game saves. Adding the code for that takes about 100 bytes, which is about a tenth of what I have left. Ugh.