Alright, here's what I have for a list of hold design tips that can potentially be used on the site:
Tips for Architects:
These are some helpful tips for those who wish to add to the growing library of places where Beethro Budkin has murdered everything. Some of what follows is copied from the DROD-AE help files, which you should also read.
1) Make sure every room is solvable. The last thing any player or architect wants to deal with is an unsolvable room. If Beethro and his sword must be in a specific orientation to complete the room, make sure there's a way back to the previous room so the player can get in that orientation. In addition, make sure you can play through every level from start to finish. You might find something unexpected while you do this, so it helps identify potential problems as you go.
2) Make sure there's a way to the exit from every room in the level. I once played a hold where the entrance was unexitable. If you plan to have a path from which you cannot return, make sure you include a scroll that warns of this in some way. It's also a good idea to make sure you can always return to the entrance, which is along the same lines.
3) Make sure stairs go where they're supposed to. Occasionally an architect might misclick on the destination for the stairs, making them return to the beginning of the hold, restart the current level, or skip one entirely. The easiest way to make sure of this is to play your hold all the way through, and make sure the right levels come up at the right times.
As of 1.6.4 there is a bug that causes some staircases to return to the beginning of the hold instead of ending it. If this happens and it looks like your stairs go where they're supposed to, then verify the stairs go to the right place and leave it alone - it's just a bug.
4) Include Checkpoints. Even if the room doesn't involve a puzzle, killing monsters is long work. Would you want to kill 500 roaches, make a typo, and have to kill those roaches all over again? As a rule, any room that takes more than about 50 moves to solve should have a checkpoint. Also, all checkpoints should be in logically useful places.
5) Aim for fun, not difficulty. Remember that people will play your hold because they think they'll enjoy it, not out of some unspoken duty. If your hold is unreasonably hard without being fun to figure out, people will stop playing it. As an easy test, play the hold yourself. If you can't get through it without becoming frustrated enough to stop playing, neither will anyone else.
6) Avoid trial-and-error puzzles. Having to restore and try option seven is no fun. Good ways to avoid these puzzles are not covering things with tar, avoiding puzzles based on specific monster movements, and limiting the number of orbs in a given room. This is a guideline, not a rule, as a little bit of anything can be interesting.
7) Avoid exploiting quirks. Don't make rooms that depend on some game anomaly you discovered by accident. For instance, if you discover that when a goblin enters a square adjacent to a roach queen on the turn before the eggs lay, one of them will hatch before the others, don't make that part of the puzzle. If you do find a quirk and just can't resist, include a helpful scroll so the player knows what's going on.
Don't have too many slashfests. Mowing down monsters can be entertaining, but doing it in every room gets really old really quick. If you really want a room with tons of monsters, design it in such a way that the player is forced to make some tactical decisions, so some variance to alternating between q and w appears. Also, if your point can be made with 50 monsters, don't use 500.
9) Don't be afraid to put parts of your hold up in the Architecture forum for people to play through. The worst thing that can happen is the players find trivial solutions or room bugs that you didn't notice, and they tell you about it so you can make your hold better. You can always post up another version later, which will be played as well.
10) Don't give incomplete levels in your hold. Every once in a while someone uploads 2 1/2 levels, where the third level is a work in progress and not actually ready for public consumption yet. This gets frustrating from a playing perspective, as you find out there was no reason for you to have spent the last 2 hours on this level you'll just have to replay in the next version of the hold. If you're offering something for download, make sure it's a finished product, even if that means only including 1 level of an eventual 20.
11) If you're uploading a new version of an old hold, and all that's changed is the addition of some levels, include a staircase in the first level entrance to go directly to the new levels. Can you imagine having to play through 16 levels to get to the new level 17 every time a new level emerges?
12) Playtest rooms as they are constructed. This seems like a lot of wasted time as you do it, but in the long-run it will save you frustration. I always test every part of a room as I make it, so if something I add suddenly makes the room unsolvable I know exactly what it is. If I had designed the entire room and only then started playing it, I would have had to decosntruct every part of the room to isolate the problem.
I hope these twelve points help you design holds that are both fun to play, and fun to make.
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Deploy the... I think it's a yellow button... it's usually flashing... it makes the engines go... WHOOSH!