GMTs 'Space Corp 2025-2300AD' by John Butterfield has a low medium complexity for 2-4 players and a high compatability for solo play. As I generally write about multi-player or two-player games, I thought it would be an idea to take a combined look at solo and 2-player games. It does seem though that GMT are more than confident on the playability for one player versus John Butterfield's mechanic, that they have included a 28 page book of Rules specifically for the lone adventurer (the multi-player rules book is only 24 pages, thus cementing this as specific a single-player game as you are likely to get).
You are in competition with other corporations to conduct missions in space and on planets other than Earth. You are out there exploring the solar system for planets and moons where you can build bases - Refineries, Spaceports, Industrial Factories, Research Stations, Bio Labs and even Attractions (DismallyWorld in Space) to tempt regular folk into taking well-earned vacations in a place where the Milky Way isn't just a chocolate bar.
Space has been divided into quadrants with planets, stars and moons that can be explored. You begin with the Spaceport on Earth and launch your rockets from there, using MPs (Movement Points) to reach other space-places, either in the same Region (quadrant) or in one you can reach; you must have enough MPs to move, cross boundary lines, and land. Certain planets, like Earth, also have a gravity cost, this needs to be added into the total MPs required..
Before you can traverse the galaxy you have to launch from Earth's Spaceport. Other Spaceports must always be built on Lagrange Points. You have a limited number of each building you can construct, so planning where you are going to land and what architecture you are going to grace it with. You must always have enough points to land as you cannot remain floating in space. Buildings have (assumed) fuel pumps whichever site you erect them on, so you never run out of Rocket Fuel (the stuff that makes space-crafts move, not the powerful instant coffee).
The lines on the map that separate the regions each contain a diamond with a number within. This number is the cost of travelling across the line and must be taken into account when assessing your Movement Point cost. You should also note that it takes one MP to launch (team rockets can launch from any space) and one MP to land.
Each player has their own personal board, their HQ, on which they can place cards to create their static abilities. These boards are double-sided and have 3 card slots on each side. One side has pre-printed Infra slots for Research  Move  and Build , the other side has all four slots pre-printed. Whichever side you are using the Research is always at  and cannot be changed. Empty slots and other pre-printed slots can have other cards positioned over them to alter the value of these abilities/actions, and all different actions, including Research, can be temporary enhanced by playing cards from your hand.
There are three eras of play and should, at least for your first couple/few of games, be played in the E1, E2 and E3, these being titles 'Mariners' which uses the space map out as far as Mars. 'Planeteers': Where your teams can begin to settle in regions past Mars and (not quite to infinity and beyond) into the Outer Limits (way past the TV series). Finally the third era is 'Starfarers' and the establishing of interstellar colonies. Together the three eras make up a time span of 300 years (or in our case, many pleasurable hours).
The board, double-sided (or triple-sided as GMT happily point out) unfolds/joins in three configurations, each marked with the Era Title. Once you have played through at least once then you can jump in and begin playing at any of the Eras. If you know what you are doing and require a tougher game over a shorter time period, then play just Era 3. If you have the time, then always play off scratch, and give yourself the added incentive of doing better than you have previously, and perhaps find different paths to follow.
Where your team (rocket) is you may Explore any empty Discovery space (Lagrange spaces can never be explored) by using the necessary number of Explore points (EPs). There are face down stacks of Discovery Tiles from which one (with the correct 'E' number) is taken and placed on the Discovery space, face up. This details what can be found, such as resources etc, on the associated planet, star or moon. There are details on these tiles along with mini pictograms (for example a blue drople indicates Water is available).
Buildings without Shielding cause you loss of profit when erected in a 'radiation zone'. Some Move and/or Build cards have two values, one for shielded and one for unshielded; the unshielded values are always higher than the shielded values, the player chooses which value to use.
There are many small complexities in SPACE CORP 2025 that require a clear understanding of what the rules' author means on every page. I found that I was occasionally struggling to get my head around a few things, but a little commonsense and reading whilst playing brought clarity. There isn't anything actually difficult to comprehend about the game, in fact the majority of the gameplay is quite transparent and straightforward; most of the game is played via the player's HQ and uses the player's intellect and deductive reasoning.
As I said earlier, I played the game as a solo player and in a 2-player competitive match, and the rules are so similar that they just blurred a little and melded into my mind. Both Fran and I (playing 2-player) decided that the map for the first Era was a little tight, offering a squeeze of options for the pair of us. With more players, those possibilities will almost certainly be contracted, game slowing, and thus require more thoughtful tactics.
I am not one for playing solo games too often, but I really did get into this, me against the mechanic bots. I actually enjoyed it quite a lot, but admit that playing the two player game, with human thought and interaction, just edged solitaire play.
£54.76 when Zatu have it in stock is a terrific price. $87.00 for the 2nd edition from GMT. £71.99 from Boardgame Guru (UK).
On Amazon UK I saw it at a quite high price but with a note saying it was for 3 year olds and upwards - I think that may be erroneous.
2 mounted double-sided 17"x17" game boards
3 counter sheets
4 (identical) double-sided reference sheets
1 double-sided Solo Player Aid
1 Business Display
4 BASIC Headquarters Displays
4 PLANETEERS/STARFARERS Headquarters Displays
3 card decks: 188 Action Cards, 18 Adaptation Cards, 14 Breakthrough Cards (220 cards total)
24 cubes and 7 orange discs