Perhaps replace all instances of "DC2" in the game's text with "DC3" and replace "Diamond Caves 2" with "Diamond Caves 3" once all of the unimplemented DC3 elements are in.
Note that I am defining "move" here as the time it takes for the player to move from one square to another.
Note that these elements are from DC5, the Steam version of Diamond Caves, but only the ones that I have seen in DC3's editor are included.
If you completely forget what some of the pictureless elements below look like, take this DC3 demo. It contains tutorial levels, which go over every element in DC3, and an editor where you can quickly view what elements look like.
Skeleton Key: Gives the player every key (whether this includes EMC keys is up to you), and an infinite amount of white keys. Worth as much score as a normal key.
Four-color door: Can be passed through once the player collects any red, yellow, blue, or green key.
Wooden door: The red, yellow, blue, green, and white doors come in wooden variations. These wooden doors act the same as their counterparts except that they can be destroyed.
Doors: All doors except the exit door are slippery in DC. This is not the case in RnD, nor EM, so perhaps fixing this would be best as a "doors are slippery" level setting.
Wall with content: DC has a lot of walls with content. Here's everything that isn't currently in RnD (some of it is things currently in DC but not RnD):
Wall with Ruby
Wall with Boulder
Wall with Nut
Wall with Bomb
Wall with Megabomb
Wall with Ship (facing up)
Wall with Bug (facing up)
Wall with Yam-Yam (moving up)
Wall with Robot
Wall with Mole (facing up)
Wall with Slime (random direction)
Wall with Wheel
Wall with Red Key
Wall with Yellow Key
Wall with Blue Key
Wall with Green Key
Wall with White Key
Wall with Skeleton Key
Wall with Dynamite (not lit)
Wall with Shield (normal)
Wall with Extra Time
Wall with Closed EM Exit
Wall with Open EM Exit
Wall with Green Amoeba
Wall with Yellow Amoeba
Considering how many of these different elements there are, it might be more practical if there was some way to assign content to individual walls instead of having all of these "wall with content" elements flooding the editor.
Narrow passages: These are completely identical to the one-way ports from Supaplex and would just be a reskin. You go in through the big end and exit through the smaller end.
Narrow steel passages: These are just the Narrow passages except indestructible and textured to look like steel.
Wall (not round): This is one of many flat walls that gems and nuts do not slip off of. There is a small indent in this wall's graphic, as if the wall was built so that objects would be caught and not slip off. Speaking of DC-style slipping...
Gems and nuts will slip off of the following normally non-slippery DC tiles:
Flat normal wall
Flat steel wall
Invisible normal wall
Invisible steel wall
Replicator corner tiles
Replicator switch
Exit
Steel exit
Conveyor switch
All tube tiles
All remote bomb controls
Teleporters
RnD emulates EM slipping behavior fine, but not DC slipping behavior: the nut, pearl, and crystal do not have the "slip from certain flat walls" option that the other gems do, and gems with said option enabled do not slip off of invisible walls, exits, steel exits, tubes, or conveyor switches. (For the EM slipping behavior to coexist with the DC slipping behavior, they would have to be separate options, given how gems do not slip off of invisible walls or exits in EM.)
Steel wall (not round): Same as Wall (not round) but steel and indestructible.
Yellow Amoeba: From what I can tell, the only difference between green and yellow amoeba is that they can have different growth speeds set in the editor. Perhaps in RnD this could be given all of the same variations that green amoeba has (BD amoeba, amoeba with content, etc.) and with all of its settings completely independent from green amoeba.
Grass (DC3): Grass grows like amoeba, but can have a different growth speed set. It can also be dug away like dirt. It does not explode on contact with ships, bugs, and BD enemies the way regular amoeba does. For clarity, this should probably look different from the EMC grass - maybe a lighter shade of green?
Conveyor belt switches: DC has some options that RnD does not. Conveyor belt switches can be set to start on the left, in the middle with the next push turning it left, on the right, or in the middle with the next push turning it right. Unlike RnD, conveyor belts in DC can be manually configured to start at a certain direction, and do not require the presence of a conveyor switch to determine which direction they move objects at the start of the level. Also, switches in RnD can be activated by falling boulders, but only the player can activate switches in DC.
Conveyor: Conveyors in DC move objects as fast as the player's normal walking speed, but conveyors in RnD move objects slower than that. Also, in DC, active conveyor belts produce an ambient droning noise.
Yam-Yam: Yam-Yams in this game (they are called "Eaters") start the level moving down instead of up, except if they are summoned into the level via being smashed out of a chest or wall with content or being spawned via replicator (in which cases they start the level moving up). A Yam-Yam summoned by smashing another Yam-Yam will be moving down when it is spawned.
Also, when a Yam-Yam eats a diamond in DC, the diamond plays its "collected" animation, and the Yam-Yam does not continue moving until the diamond is fully collected.
Emerald Gate: Every time you pass through it, an additional gem is added to the amount of gems you need to open the exit. However, if you are at zero gems needed, passing through the emerald gate cannot bring it back up.
Growing walls: DC also has some growing walls that can only grow in one direction, as opposed to two or four. Growing walls in DC grow at the speed of a walking player, but growing walls in RnD grow slower than that.
Switch gate/time gate: The open/close animations for these gates are much shorter in DC than they are in RnD. This means that after opening a gate, you can go through it near-immediately in DC. Also, they use the menu door sound for opening and closing, instead of the long exit door sound. In my opinion the menu door sound is more fitting for these gates; the exit door sound should only be used to indicate something really important to completing the level (i.e. the exit door opening).
Time gate wheel: In DC, if you spin a time gate wheel, then spin other time gate wheels while the first wheel is still spinning, all wheels will stop spinning once the first wheel stops spinning. In RnD, this is not the case, and you can extend the duration for which a time gate is open by spinning multiple time gate wheels.
Switch gate switch: In DC, these are slippery and nothing can switch them except the player.
Tubes: The tubes in DC and the tubes in RnD are nearly identical (although the RnD tubes are reused from DX Boulder Dash, I'm guessing DX Boulder Dash reused its tubes from DC2), except... you guessed it, the player can't be seen inside of RnD tubes. Navigating through tunnels can be much harder if you don't know where you are. I would recommend making the tubes partially see-through like this: viewtopic.php?f=5&t=2583
DC tubes also make rattling sounds when you walk through them.
Boulders/bombs/etc.: I just wanted to point out that the push delay for pushable objects is much different in DC than in RnD. In DC, there seems to be about a 50/50 chance for the object to move instantly when pushed on. The push delay can also get larger than in RnD, up to at least 1 second (6 moves). I don't have exact numbers.
Contact mine: Once it's activated, it explodes in a 3x3 radius after 1 move. It activates when it's fully adjacent to an enemy (including amoeba) or the player, or when it's hit from above by a falling object. Amoeba drops do not activate the mine unless they turn into regular amoeba within the mine's range. Like bombs and remote bombs, it will prematurely explode if it is caught in another explosion.
There is a specific peculiarity I've noticed with contact mines: if, on the turn the mine explodes, a player is in range of the mine's explosion but is moving to a non-explosion tile, that player will survive; but if an enemy that moves at the same speed as the player (such as a ship, bug, or eater) tries to do that, it will not survive. I suppose that applies for all explosion tiles.
Dynamite: DC5 (Diamond Caves for Steam) features a little bar below the player that fills up while you hold down the "drop dynamite" button so that you know how long to hold before the dynamite is dropped. Personally I thought this was a very good way to convey that you have to hold down the dynamite button and not just press it, and it would be a nice feature for RnD to have.
Dynamite (lit): DC3 allows pre-placed lit dynamite in a stage much like RnD, except you can also select the fuse length (whether it explodes in 4 moves, 3 moves, 2 moves, or 1 move)
Steel signs: DC3 has some signs that are not in RnD or not properly represented. Here's a comparison:
Although the heart sign exists in RnD, it is one of the hidden Frankie Goes to Hollywood signs that cannot be accessed except as user-defined elements. It also has different shading than the DC heart.
Although the arrows exist in RnD, they are destroyable and do not actually appear on a steel wall.
The radioactive sign already exists in RnD's DC2 category, but it is triangular instead of being circular.
If the Player 1 and 2 signs are put into RnD (as yellow Rockford and red Rockford, of course), there should also probably be Player 3 and 4 signs.
Also, the guy on the handicap sign has an arm in RnD but not in DC... but that's just nitpicking.
Magic steel wall: Same as DC2 magic wall, but indestructible. Perhaps steel variants could also be made for the BD and EM magic walls.
Wall (round with point): Slippery. If a nut falls and lands on it, the nut will crack. It's that simple.
Steel wall (round with point): Same as Wall (round with point) but steel and indestructible.
Shield (normal): RnD treats stacking shields differently than DC. If you collect a 3-second shield (for example), and then immediately collect another shield, in DC your shield time would be reset back to 3 seconds, but in RnD the shield times would add and you'd have a shield of 6 seconds.
Another thing DC5 does with this that I like is showing how much shield time you have left with the shield ring gradually disappearing, instead of just flashing quicker like in RnD's case.
Removable DC2 mine: In DC, if the player has a shield, this tile can be dug through as if it were regular dirt. In RnD, this tile can only be removed by snapping, and will be treated as a solid tile if the player tries moving into it while using a normal shield.
Replicator: There are four colors of replicator: red, yellow, blue, and green. Each colored replicator has five parts, all indestructible, and the corner parts are considered slippery for gems and nuts. The only part of a replicator that actually does any spawning is the bottom-right tile, which spawns the replicator's selected element to the left of itself. This is a fully assembled red replicator (you could take every part but the bottom-right off and it would still work):
Replicators spawn elements and are controlled by respectively colored switches, like magic balls. Unlike magic balls, their generation delay can not be configured and is always 2 moves, and they can not kill Rockford if he is blocking the space in which an object would generate (unlike RnD magic balls, anyway. EM magic balls never kill the player). Each replicator spawns one type of element over and over, and it will spawn that element out of the empty space that its parts form over (the bottom middle space). Which element it spawns is configurable. In DC, you can also configure whether each replicator starts the level activated or not.
Light Barriers: Think infinitely fast one-directional growing walls that can be toggled on and off. Like conveyors and replicators, these come in red, yellow, blue, and green, each color of barrier emitter has a respective switch that can toggle it, and each color of emitter can be configured to start the level in an enabled state. The barriers can freely pass through perpendicular barriers, but will be blocked by parallel barriers. If two barrier emitters facing one another are freed of obstruction at the same time, the barriers facing left or up will override the barriers facing right or down, but the reverse is true if the two barriers are activated at the same time. It's hard to explain, so here's some gifs:
(Yes, those player movements are synchronized in the second image.)
Barrier emitters, barrier switches, and the barriers themselves are all slippery, though they appear to be flat.
Remote Bombs: Remote bombs can be moved around either by pushing them (they have zero push delay), or by pressing one of the "remote bomb switch" tiles. Very similar to balloons and wind, except they only ever move one tile at a time. They explode if a "remote bomb switch (ignition)" tile is pressed, or prematurely if crushed by a boulder or caught in another explosion. Also, they are slippery.
Postcards: DC allows for up to eight types of postcards in one level. This means four new types of postcards would be introduced to RnD. Might I suggest they use the same coloration as the four EMC-exclusive keys and doors?
Teleporters: They come in the classic four colors: red, yellow, blue, and green. Only players can enter them. Teleporters work best when there is exactly one other teleporter of their type in the level - a lone teleporter will just act like a steel wall, and if more than two teleporters of the same type are in a level, the first two will link and the extras will act like steel walls.
When you press against a teleporter, if the matching teleporter is unblocked, you will instantly appear at the destination teleporter - there is no animation for walking into the entry teleporter - and be walking out in the direction you pressed at the entry teleporter. I am guessing this is because the designer wanted entering and exiting teleporters to be as fast as entering and exiting a door, but for some reason could not just speed up the player like when passing through doors.
If you press against a teleporter that has a valid destination teleporter, but that destination teleporter is blocked in the direction you're trying to move, you'll just uselessly shuffle against the entry teleporter for one move and stay in place. Teleporters are declared blocked the same way doors are considered blocked, so you can't teleport onto a diggable or collectible tile.
Quicksand: Whatever the quicksand speeds are in DC, they don't seem to match up with the quicksand speeds in RnD.
Here's the DC speeds: no quicksand, quicksand, and slow quicksand.
Here's the RnD speeds: no quicksand, fast quicksand, and quicksand.
From what I remember, RnD treats fast quicksand in a way it probably should not be: the rock does not travel through the quicksand itself any faster than it would in normal quicksand, it only has a faster animation for entering and exiting the quicksand. This may be why the quicksand speeds shown above are not synchronized.
Magic wall reset: A button similar in appearance to the DC2 light switch. Pressing this tile after the magic walls have disabled will cause them to reset. You can then push a convertible onto the magic walls to re-activate them. (Whether this should only affect DC2 magic walls or BD and EM magic walls as well is all up to interpretation.)
Hammer: Collectibles similar to white keys. While you have at least one hammer, snapping at any of the following tiles will create a 1x1 explosion on that tile and use up a hammer:
Wall
Wall (invisible)
Wall (round)
Wall (round with point)
Wall (not round)
Magic wall
Growing wall (any type)
Narrow passage (any direction)
Wall with content
Chest
Chest: There are eight types of chests. Each type can be configured (much like a replicator) to contain a certain element. If the chest is exploded specifically with a hammer, it will leave behind its selected element. Chests are slippery.
Slime: The slime moves about twice as slow as a Yam-Yam - so slow that if it's directly below a boulder and moves down, it can be crushed by the boulder in mid-air. It cannot harm the player except by its death explosion. If the slime moves into the following element, it will absorb it as long as it does not already have something absorbed:
Any gem
Shield (normal)
Extra Time
Dynamite
Hammer
Any key
While it has something absorbed, that absorbed element is shown inside of the slime, except transparent and as a small graphic. Once it is smashed by a rock (or killed in any way that would cause a Yam-Yam to leave behind its contents), it explodes in a 3x3 square and leaves behind the absorbed element in the spot that it died.
Level border: DC does not automatically place a steel border around levels like RnD does. The level border can be touched, although it is completely indestructible.
Wraparound: DC allows for horizontal wraparound, vertical wraparound, and both types at once. The size of a level determines how far it goes on before it wraps around. If this is implemented, the camera should allow a player behind the wraparound point to see what's on the other side of the level.
