Detective David.
David wrote:* What do the buttons with R and C do?
To start with "c", it allows for the modification of the prince's palettes.
As for "r"... As you know, there are more block combinations possible than just those that comprise the tiles on apoplexy's tiles screen. While apoplexy has a custom tiles screen, its usability is limited with PoP1 for SNES, because: a) the application uses premade images, and b) there is no overview of blocks. On top of that, the automatic conversion of tile corners only works if the application knows about a block's 'sister blocks'. Furthermore, I'm deliberately limiting certain build options to keep things easy to use. And, finally, I am of course limited by my own coding capabilities and energy, time, et cetera. I've thus been looking through other tile combinations and came to the conclusion that the vast majority of custom tiles only make sense in combination with others. For example, in the umber environment (brown dungeon), you would rarely use just the dragon head's nose - you'd use the entire dragon head. Similarly, in the silver environment (grey palace), it makes sense to use one or more full bridge arches - not just one of its pieces. Therefore "r" provides a screen with room templates, to replace entire rooms, that can then be customized further. An example is the room with the (red/blue) knight.
David wrote:The only object I don't see is the lava. Maybe it's that?
It is. To keep things consistent it's also on the tiles screen for the blue environment - not just with lava. (Similar to how the teleport marker is on all tiles screens, even though it's only usable in green environments.) It looks like a regular tile, walking over it is possible, but falling on it from any height means instant death.
David wrote:* I guess the potion with circle is the warp (see also the last screen), and so the one with X is the slow-fall?
Correct. The X is a bird/plane, although that's difficult to see on the tiles screen. Although, now that I've written that, you'll probably see it.
David wrote:* The numbers mean the animation groups?
Yes.
David wrote:* The green circle is the destination for the warp potion?
Yes.
David wrote:* What is that long bar on the left side of the Save button? A progress bar, maybe?
It is a status bar. To give an example: when the mouse cursor is on the area with the green circle, the status bar says: "Target destination of the warp potion."
David wrote:Is this [automatic conversion] what you mean?
It is. The tile that's being placed depends on what's under the current location. Also, the tile above the current location is being updated if necessary. Sometimes both need to happen. For example if a wall is being added underneath a floor and above a pillar.