AI War has been around since 2009 or so and is indie dev studio Arcen Games' flagship product. It's a masterpiece that plays by its own rules. It's the Dwarf Fortress of fleet command RTS games really - the options are overwhelming especially with all the expansion pack DLC content. Start simple and grow into it. You can supplement the game or make completely game altering changes including an alternative win scenario and an extensive campaign mode. If you overestimate your ability with a difficulty level that's beyond your experience you will NOT have a fun time. OTOH, it may be a very short game :-) There are strong elements of RTS, tower defense and grand strategy, even a bit of a twitch factor in the combat and fleet handling. It does them all really well and it's a unique formulation. The downsides are the steep learning curve (ease into it), the brutality of some of the optional features can create nasty surprises, and games of AI War are LONG - expect to spend 14+ hours on even a small campaign. Also it's pure 2D, which may bug some folks, and the graphics quality vary from amazing and detailed to uninspired white blobs, but they all do the job. I love the soundtrack but some don't care for it - a lot of moody piano/orchestral scores that are almost too good and too melodic to sit well in the background. In short - it's amazing, get it.
Short version: At $5 it's tough to go wrong and you get a lot of depth and decent replayability for the money. This was my second Arcen game after AI War, purchased on Steam shortly after it came out several months ago. It captures the 'roguelike' feel in the early game extremely well and offers distinctly different feel to combat through the several classes of mech which you will need to pilot through the semi-random, procedurally-generated levels. If you're into the "retro" motif, the music and graphics definitely will be appealing. Unfortunately as the game progresses you can get mired in needless complexity as the loot piles up, and after a couple of playthroughs the basic patterns of level design does become quite samey. That said, an early DoomBot encounter with a low-level party will cause you to lose sleep (and likely at least one team member). The strength and replayability lies in the way you combine weapon types and use the strengths of the various classes, though in the early game min-max of the limited loot supply is extremely important. Late-game, loot management becomes a real chore and 1-2 hrs of spreadsheet-like tedium rewards you with a 2-3% increase in a couple of vital stats if you're lucky.
