When I started working on Spectral Dungeons, there didn't seem to be many roguelikes for the Spectrum. A search for "Rogue" on World of Spectrum yields only one title that might be a port of the eponymous game, and the screenshots don't look especially promising.
It was only recently that I became aware of another. Ossuary is just the most recent release from UK developer Cyningstan, and it's an incredibly colorful game that fits in only 16K of RAM and can be played with just a joystick. Otherwise, however, it's interesting to see how many of the design decisions are similar to those I made.
At some point in development, I decided that in my next game there will be just one level generator and you will only be able to go down -- what roguelike afficionados call "ironman mode". That's exactly how it goes in Ossuary, except the premise doesn't support it and the level generator is much simpler. There is also only a handful of items and monsters, but at least the author managed to squeeze in an extra tactical layer, in the form of magical weapons that use a different attribute and can hurt supernatural creatures. That's something I considered and discarded. Maybe I shouldn't have. Another concept I considered and discarded was the presence of gold in the dungeon, which in the absence of merchants is only useful for keeping the score. At least here the premise does support it.
But the most obvious similarity between Ossuary and Spectral Dungeons is the basic setting. You know how the most common criticism directed at dungeon crawlers is that all those underground mazes make no sense? I thought I was being original by setting the action in a catacomb, which immediately explains where all those undead come from, as well as why there are weapons, armor and gold laying around. It would also explain all the traps if I had any in my game, but I don't. Clearly, though, it was an obvious idea. In retrospect, it's surprising that more games aren't using it. Apart from those set in pyramids, I guess.
Of course, in neither game is there any attempt at a line of sight algorithm. Seeing everything in a fixed radius is simply good enough!
Last but not least, I want to point out a contrasting design decision. In my game, I went with the traditional one-key-per-command interface, except with few enough of them to be displayed on one line. Ossuary, on the other hand, uses a menu-based approach. That allows for more commands without complicating the interface, but it's also error-prone when the default action for the present context is not what you want. Luckily, here that's only mildly annoying instead of fatal. (Unlike in Barbarians, a strategy game by the same developer.)
Ultimately, though, similar constraints lead to similar solutions. The differences that do exist stem from the fact that I'm actually new to ZX Spectrum development, and filtering my knowledge of roguelikes through modern design sensibilities. I'm also aiming my games at people who may not have owned a Spectrum back in the day, and don't understand why their PC keyboard behaves oddly in an emulator. But the goal of making a fun game is the same for everyone, and I have much to learn from old hands.