Hack! Hoard! ... Mourn.
In this dungeon, time only moves forward when you do. You can take your time to solve problems instead of just spamming "attack" and "drink healing potion" buttons.
With over 250 different types of items to be found, there is no shortage of solutions to problems. With over 100 different types of monsters, there is no shortage of problems either! But this is no puzzler - you will have to fight your adrenalin and use your sword or staff as much as your inventory. It's not a game of plodding to the end and winning (though it is winnable), it's about experiencing the attempt... and learning lessons that will help your next valiant attempt!
You start with your choice from 8 character classes, each with different starting equipment and stats, but the game you play depends on what interesting stuff you find. Maybe you'll find a great spellbook and put all your efforts into turning your uneducated knight into a master battle mage!
The procedurally-generated dungeon and vast array of possible items gives immense replay value. Some games you'll find a good weapon early, other times you'll rely on wands or potions or spells.
The multiplayer mode is a little crazy. Each player is actually in their own instance of the same dungeon. Players encounter the same monsters, but fight them individually. In co-op mode, players find different loot and may trade with each other whenever standing in the same place. In competition mode, players find the same loot.
Run the installer, run the game, enter your key.
Tweakable in Options/Graphics.