Added basic tile, block and scene editing support
Added initial event editor.
Stage 1, 3, 4, and 6 will load up with varying graphics problems - more in the later stages. The problem appears to be that the game reloads most/all tiles in VRAM to transition to bosses and mini bosses. So the editor would need a way to support this probably through some keys to toggle between those transitions.
The tile, block, and scene editing is mostly untested. I was able to make some basic changes to stage1.
Unfortunately, the events work completely different than SCV4. You can't add or delete them, yet, but you can change some basic position and type parameters. For example, Id=$F are the drops and for SubIds, $1=spread, $2=crush,$6=invincible bubble, $7=bomb, etc. There are lots of custom events and the game is heavily scripted in parts. Stage4 seems to be completely scripted and doesn't have individual events (or they are stored and executed differently). The events look like they are grouped into $100 pixel wide groups and in the ROM are stored as relative positions to that. The position of the scene is added to the xpos to make the absolute value shown in the editor. The relative position of the event (negative vs positive) can determine which side of the screen it spawns on. How exactly the events work is still a mystery, but it's possible to make some basic changes now with trial and error.