Desktop Dungeons is a quick-play dungeon crawler from QCF Design that boasts short, 10-minute missions that allow you to get your gaming in during your coffee break.
Each randomly-generated dungeon gives you roughly 10 minutes of gameplay. You can generally speed through each zone in far less time than that, but there is some level of strategy involved if you want to keep your character alive.
The goal of Desktop Dungeons is to build your kingdom by completing a series of dungeon crawls. It's basically a very loose take on a kingmaker campaign you might find in Dungeons and Dragons.
Where it differs is that you can not only complete an entire fight a few clicks, but you regenerate health and mana by uncovering dark areas of the dungeon. The more you explore, the more you regenerate.
One trap I found myself falling in to constantly was that I would explore the entire dungeon before taking on the enemies I found. This left me vulnerable as damage taken from one enemy couldn't be recovered unless I had some potions handy.
As you explore the dungeon, you can pick up power-ups that add spells to your list of weapons against the foes you come across. Some spells allow you to demolish or build walls, while others have more practical battle applications. My personal favorite allows you to hurl a fireball at your opponent to weaken them before you go in for the kill.
Desktop Dungeons is unforgiving, and difficult to master. At the same time, it's quick and easy to play in bursts of about ten minutes or less. This makes it a good choice for hardcore gamers and casual gamers that aren't afraid of a challenge.