Posted: 11/26/08 Legend of Zelda done with procedural generation and collectible cards, part 1. Play through a series of challenges, or simply create your own, for an infinitely replayable game.

This is the first of four entries detailing a very specific game idea that sort of draws together a lot of the procedurally generated content stuff I've written about before, as well as some other favorite recurring themes of mine.

To describe the game simply, it is a retro-styled 2D action adventure game, very similar to the original Legend of Zelda, Golden Axe Warrior, or the Neutopia games. There is an overworld made up of distinct screen-sized blocks, a bunch of dungeons to go through, and tools that help you go through it. The difference is, this game is randomly generated through a set of collectible cards. Play through specific challenges, or build your own decks to create a game that is tailored to your specific tastes (or even to challenge your friends).

The hope is that the procedural engine operates as something of a middle man between purely provided entertainment and a tool of creation. Using cards gives player some input into the procedural generation of each dungeon and world, providing the ability to not only experience the game fresh each time, but also to customize it to their own preferences (you could play a short Zelda with only 4 dungeons, or may an epic Zelda with 200 dungeons in a massive overworld, or a Zelda that takes place entirely in a forest, a Zelda that has no combat, or a Zelda with such high difficulty that only the most hardcore need apply). The more you play, the more options you have.

There are four sets of cards that define your experience: Player, Town, Dungeon, and World.

Player cards are essentially loot, though it must be pointed out that this is not a stat-based RPG. Rather than one sword being slightly better than another, they have special properties, like a fire sword or an orc slayer which does double damage to orc enemies. Each player card has a point value, and the player may only bring with him a limited amount of loot with him into the game. All player skills (such as magic), weapons, armor, items (healing potions), are player cards that can be made available at the start of the game.

Town cards are used to create a central town area that the player starts in. Like Player cards, a town deck is created from a limited amount of points up front and is brought into the game. The town provides shops and services that are customized based on which cards are in the deck and how they are placed at the beginning of the game. A certain random assortment of Player cards not in the Player's deck will be made available through the town shops. Also, optional quests and missions may be made available through specific villagers.

Dungeons are defined through Dungeon cards. Basically, once a theme, layout, mid-boss, and boss are selected, then the encounters, monsters, and treasure are selected from the deck and randomly inserted into the dungeon. When building your own Dungeon deck, filling it with just enough cards will ensure specific features are found, or overfill it with many extra cards to increase the randomness of it.

The Overworld is a directed tour through a bunch of connected zones, with each zone featuring a single dungeon. It is built in a similar fashion to dungeons, but has no bosses or specific puzzles. Instead, it is built around open exploration with respawning enemies and lots of secrets to be found.

Dungeons and the Overworld are very similar and differ mainly in scale. They may both be modified with quest cards which can add optional objectives, increase the difficulty, or even just mess with your head. For instance, a dungeon with invisible enemies, a score bonus for not dying, or a quest to locate twelve crystals hidden throughout the overworld. These quests may be applied manually or automatically by specific townsfolk.

The game itself is split into two distinct attitudes, challenges and customization. A challenge is a specific deck (or set of decks) that are predesigned by the game creators that reward unique cards or points that can be used to buy cards. A challenge could be a single dungeon using a specific Player layout, or a limited point value for Players to provide their own equipment, or a full overworld and set of dungeons.

The point of challenges are to provide, first, tailored experiences that feature cards and decks that the player may not yet be capable of using, and second, to give a directed, rewarding experience to players who don't actually care about the card collecting and customization aspects. Challenges should be built around novel uses of the cards, showing the possibilities of the deck building system. A challenge can be something short and immediate or a fully in depth experience that features as many possible gameplay mechanics and quests as possible. The vast majority of player and town cards can only be unlocked this way (while dungeon and overworld cards can be collected outside of challenges).

In addition to the directed challenges, players are also free to experiment and build their own infinite number of games, either to play themselves or to give to friends as challenges. Even if the player never dabbles in this aspect himself, the challenges provide enough incentive to see the procedural generator in action, and to experience the game in a multitude of different ways. The customization aspect is mainly there for players who want to mess around with deck construction and see creativity as its own reward. However, the generator should create fair and balanced experiences, such that the player can still be rewarded with appropriate purchase points for playing through custom games.

For instance, if the player decides to make all enemies have only half health through a quest card, the quest card will apply an appropriate score modifier to that particular dungeon. Deck creation should be fairly free from exploit, given that customization is done through pre-built components. If players do something stupid, the generator can make up for it easily by ignoring specific card choices and replacing them with more appropriate ones from the player's collection.