Ever since I got an Android tablet, games that I can play when I have a just a few minutes (such as during commercial breaks of a baseball or football game) have become much more interesting. I've tried quite a few, in various genres, and Star Realms is one of my favorites.
Star Realms is a space-fleet combat deckbuilding game. For those not familiar with the genre, deckbuilding games start each player with a similar basic card deck. Players acquire more powerful cards throughout the game, improving their deck in the process, eventually using it to defeat their opponent. One game set provides all the cards required to play, and generally expansions can be added for more variety. (Not to be confused with collectible or trading card games, in which each player builds a deck beforehand, using their own card collection.)
There is a physical version of the game, but I've played Star Realms exclusively via their digital versions. Buying the game once provides access to PC, Android, Mac, and iOS versions. I mostly play on my Android tablet, but it's nice to also have the PC version available. A single account is used to log into all of these, so your in-progress games can be played across devices.
The actual gameplay is pretty standard for the deckbuilding genre. You start with basic ship cards, primarily providing trade points, which you use to purchase more ship and base cards. Ships provide their effect for one turn; once you've played a base, it stays in play until removed. Both players get the same purchase options, so a ship or base that you buy is denied to your opponent...and vice versa. The ultimate goal is to obtain ships and bases that produce combat, which you use to attack your opponents "authority" (basically, life points). First player to reduce their opponent's authority to zero wins.
Star Realms has a single-player campaign, which I found to be moderately interesting and a good introduction to the gameplay. The story won't win any awards, but it works fine to add a little color to the campaign. The regular mode is fairly easy to complete. There is also a hard mode, which is mostly moderately difficult...and in one or two places, extremely frustrating due to bonuses given to the AI. Completing the hard campaign unlocks new avatars for your online account - whether that's worth the frustration is up to you. You can also play non-campaign games against the AI, which is fairly competent. A good player can beat the hard AI fairly regularly, but it will win some, too.
A single multiplayer game of Star Realms generally takes somewhere around 15-30 minutes, but I almost never play one in a single sitting. That's because the digital game is designed for asynchronous online play, where you play one turn at a time against a remote opponent. Occasionally you may find an opponent to play "live" with turns being taken almost immediately - there's even a 3-minute turn timer mode for this. Most of my games, though, are with friends with differing play schedules (and often time zones) where we may play only a few turns a day.
Besides the base game, there are two additional Star Realms expansions: Gambit and Crisis. The Gambit expansion adds a new type of card which starts the game in play and can have huge effects the early game. It also adds some new ships and bases, which were originally promo cards in the physical game. The Crisis expansion adds new ships and bases. Both expansions add more single-player campaign missions as well.
I find the game to be mostly well-balanced. There are very powerful cards, certainly, but they generally have the highest costs as well. Luck of the draw plays a large part in determining games, of course. Players have to choose from the cards available for purchase, and if the good stuff mostly shows up on your opponent's turn, that's just bad luck. Over a few games, that usually evens out. The only really unbalanced aspect of the game is the Gambit expansion's starting cards, some of which are much better than others. If the shuffler happens to deal good Gambits to your opponent, you're in for a rough game. You can simply choose not to use those, though, if it bothers you.
Star Realms is one of those games that fits perfectly into little slices of waiting time. Commercial breaks, waiting on something to cook, a few minutes before it's time to leave to go out, etc. I have a lot of fun with it, especially playing with friends in casual leagues that we organize almost every month. Feel free to challenge "ineffablebob" if you're looking for a game!