It's a Missile Command situation: comets and bombs plunge from alien skies toward your base, and you need to defend yourself before you're wiped off the planet. Your defenses come in the form of cards: laser cards and missile cards, primarily, in this turn-based game from developer Nathan Meunier. Missile Cards is a bit of a casual game in that it's easy to learn and playing a hand only takes a few minutes. But it's tough challenge, and winning even a few consecutive hands isn't so easy.
Your base has a main module, which begins with a few ticks of health, and two sub-modules on either side, which can each take one (non-nuclear) hit before being destroyed. Cards—which represent both the falling threats and your defenses—cycle through an airlock, one by one. When a threat card, like a comet or bomb, reaches the right-hand slot, it appears in the sky over your base and begins to fall. Your defense cards, meanwhile, need to be picked up and placed in one of the four empty slots above the threats. It takes a few turns for your defenses to charge (there are also battery cards you can use to fill them more quickly) before they can be launched to destroy the threats.
There's an enjoyable bit of strategy involved in defending your base. If a two-point comet is about to hit your base, and you've got three points of health remaining, should you use your four-point missile to take it out? Or should you let it hit, in case a four-point comet appears later? Discarding cards can power an unlockable laser defense weapon as well, so there are times when it makes sense to throw away a powerful defense that needs time to charge in favor of powering your laser for a quick strike. You can also collect extra points with a tractor beam card, but that beam needs to be charged (so it'll take up a defense slot for a while) and takes a turn to use, which is risky if there are a lot of threats incoming.
Strategizing is fun: it's satisfying to plan the use of your cards carefully and a relief when a risky gambit pays off. However, Missile Cards can often feel unfair, such as when there's a long line of threat cards cycling into play and you simply haven't had enough powerful defense cards to fend them off. I guess that's just card games in general: You can't win every hand of solitaire, right? A string of losses, when I never have even the slimmest chance of winning, does put me off a bit, though.
There's also a progression system, and earned points can be spent on upgrades. Some are card-based, like a missile that can be manually targeted at the threat of your choice (typically, defenses will attack the nearest threat), a base-repair system that can restore modules over a few turns, and more powerful cannons and energy weapons. You can also slowly add to the starting health of your base, unlock a forcefield, and add a base-regeneration power. These upgrades take a long, long time to earn, as points for upgrades are doled out very sparingly, so you'll need to play lots of hands before you can become a Missile Cards powerhouse.
But it's easy to play a lot of hands: each round only takes a few minutes, so it's perfect for short and mostly sweet gaming during your breaks, at lunchtime, or when you've got a few minutes to kill. Missile Cards is built with GameMaker Studio and has a nice retro feel: attractive yet simple graphics with a catchy chiptune soundtrack. You can pick it up on Steam for five bucks.