Desktop Dungeons is a medieval fantasy rogue variant game with full 2D graphics, music, and sound. The purpose of the game is to defeat the boss of a selected scenario or die trying.

Race and Class
The player must first select a race and a class for the character. Basic races consist of human, elf, dwarf, halfling, and gnome. Each race has an ability to convert glyphs into a specific attribute (e.g. humans convert glyphs into attack bonus). Glyphs are magical runes/spells that are randomly placed in the dungeon. Basic classes consist of fighter, thief, priest, and wizard. Each class has specified advantages and disadvantages. All classes are capable of melee combat and the use of glyphs (magic). Additional races and classes may be later unlocked.

Combat and Leveling
Combat consists of the player bumping into an enemy, each turn identifying the amount of health subtracted from both parties, which may be continued until one of the parties die or if the player retreats. Unlike other similar games, enemy units here do not move nor do they attack unless attacked first. The level experience of an enemy is always seen to indicate how strong the opponent is.

Leveling up occurs when the player has killed a sufficient quantity of enemies (e.g. 0/15). Acquiring a level allows the player to engage with enemies of the same level, otherwise difficult to defeat.

Deities
The game introduces several deities available for worship when the player manages to reach one of their shrines. Deities offer bonuses, some with disadvantages, most with certain consequences. In order to gain bonuses from a deity, the player must gain favor by increasing piety. Piety is achieved when the player commits certain actions, which may be revealed later when the action is done. Committing an action that displeases a deity, will subtract the piety. Having piety lower than zero may invoke celestial wrath. Worship may be changed from one deity to another at a cost of piety. Deity worship is optional and not required to finish a scenario.

Exploration
Environments are randomly generated and shrouded in a fog of war. Items and monsters are randomly placed. Unexplored regions will become revealed when player approaches it. Revealing unexplored regions also regenerate health and mana per revealed tile.

When a scenario is completed by defeating all the bosses, the game ends. Completing a scenario may unlock additional scenarios, classes, new monsters, or other bonuses.