To be frank, I don't care much for them, and I don't play them much. there have been a few I've found interesting or impressive - namely Friday, by Friedemann Friese, and Pocket Civ, by BGDF'er Scott Slomiany (for which I contributed a resource mechanism). But for the most part, they're just not my thing.
I worked on the solo variant for TMG's Harbour a bit, and I worked on development for Dungeon Roll as well, which is basically solitaire. Not being a fan or a player of solo games, I'm not sure if my work in those areas really went in the right direction or not.
I've never really been interested in making a 1-player only game, or working on solo modes for my multiplayer games. If a fan is interested in making a bot to play Eminent Domain against, or a solo variant that doesn't require a "dummy" player, then more power to them!
But for some reason I was thinking about solitaire game the other day. I was thinking about a deck of cards that you would shuffle and hold in one hand like Flip City, and like Flip City you would look at the information on the back of the top card and decide whether to play it or not. More specifically, you would decide HOW to play it.
Since it's apparently my thing, I decided to use planets, resources, and upgrades... though this time I sort of had Terra Prime in mind rather than Eminent Domain -- maybe because I've been thinking of Terra Prime's upcoming return as Eminent Domain Origins :)
So you would look at the top card of your deck and you would decide whether to play that card as an upgrade (to make use of the upgrade text), or load it as cargo onto your ship somehow to be delivered to another planet, or flip it over and place it planet-side up in your row or network of planets -- like exploring, only it would probably tell you what type of planet it is on the info side of the card.
The idea would be that you're building some kind of network, and then shipping cargo of some kind through that network. Originally I thought the network could grow like a lattice -- in many directions, making a sort of hex grid out of cards. But maybe a simpler version is that your network is simply a line of cards from left to right.
Rather than actually having a pawn that traverses the network, perhaps what you're doing is trying to set up a line that will score well, and what you score is the cards you've saved for cargo (rather than put into play). In a way this scoring lines in an array of cards is similar to Arboretum, which I played once, and was reminded of last night when I saw some folks playing it. In that respect maybe a lattice-style network would make more sense, and I could use a scoring system reminiscent to (but hopefully less byzantine than) Arboretum's.
I figure that the planets should have types that are important, rather than needing to take a delivery to a specific planet, thereby making things a bit more flexible. In addition, I figure some cards would have hostile aliens rather than planets, which you would fight in a way similar to Terra Prime. Rather than adding dice to the game however, I would simply put a die icon on each card with some value, so looking at the top card of the deck you'd see the current "roll" value, and if I wanted to generate a new value, I could instruct the player to cycle that card tot he bottom of the deck and reference the new roll value on the new top card. I tried to utilize this type of roll aspect in a different game I never got around to finishing, and I always liked the idea of it...
So as you play your cards, one at a time, you would choose whether to use them as upgrades, or cargo, or to build your network. Some cards may have a cost, which could be paid by removing the next card in your deck from the game - thus that card would never get played... so paying a lot of costs would reduce your potential score, as well as deny you access to those particular cards.
Maybe a simple way to score would be to do it all at the end (like Arboretum), so a player need not record timing or order of cards played. Maybe any cards remaining in your deck count as cargo, and each one scores based on how you've built your network.
I started off by saying that I'm not fond of solo games. If this idea turns out to work, and be a fun and relatively simple to play solo game, perhaps it could be made multiplayer simply by adding a drafting phase in front of the solo game play -- so 2-4 players draft cards from the entire stock into their personal, then run through their decks making their own decisions as to how to play their cards. Perhaps there's just 1 big draft and then players play out their cards until they're done, or perhaps it's an iterative thing, where cards not played are set aside than hen mixed in with the new cards obtained in the next draft phase.
It's an interesting idea, and I'll let you know if I put any more thought into it.