Incursion is a freeware roguelike (meaning a text-map, turn-based computer game featuring character growth, permanent death and an emphasis on strategy and gameplay depth) game based on (but not strictly adherant to) the mechanics of the d20 system made available under the Open Game License by Wizards of the Coast -- the same rules system used by the popular tabletop roleplaying game, Dungeons & Dragons.

Character Design: Most roguelikes focus on playing a character, with the wealth of that character's power in the items they find. However, Incursion places a greater emphasis on the design of a character, much like the d20 system from which it inherits. In order to succeed, a player must not only play their character intelligently, but also build their character intelligently, choosing effective classes, spells, feats and abilities.

Diversity: Hand in hand with this is the idea of diversity -- that different character types in Incursion should play in very different ways, making the game a very different experience when playing, for example, a dwarven evoker worshipping Ekliazeh or a lizardman bard worshipping Hesani.

Mechanical Depth: A very strong design goal in the creation of Incursion was the translation of the mechanical depth of the d20 system into a computer game setting. Commercial games have frequently ignored a great deal of the complexity of this system when they adapt it in order to simplify it to a reasonable degree. The fundamental challenge of Incursion was to try and provide a level of mechanical richness comparable to that of the tabletop game, even though the rules aren't all the same. Decide for yourself if we've succeeded!

Next-Generation Religion: Crawl was the first roguelike game to introduce what we've taken to reffering to as next-generation religion into the roguelike arena: gods with distinct personalities, abilities, weaknesses and taboos. Incursion follows in this model to try and present a pantheon of dieties that interact with, bless and punish the player, all in accord with their own ideology and areas of influence.

Extensibility: Incursion was intended from the beginning to be a big game, and its framework has been laid with extensibility in mind. It contains a compiler for its own bytecode-based programming language, IncursionScript, allowing the defining and grouping of resources (game elements such as monsters, spells, dungeon terrain and character classes) into modules, and an event-based architecture allowing customized behaviour to be attached to any resource.

Rapid Play: Incursion opposes "scumming" and other play techniques designed to grant benefit through repetition or boredom. All monsters are dangerous, to some extent, to the player. There are only 10 dungeon levels in the Assault on the Halls of the Goblin King release, and meaningful treasure is generated only once on each -- staying on a given level will not create more treasure. This, combined with several other factors, serves to bring Incursion closer to the "replay many quick games, but think always" ideal the roguelike paradigm encourages.