Code Kata for a two-player trading card game loosely based on Hearthstone - Heroes of Warcraft®
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Latest commit 76f3b51 Oct 13, 2016 @bkimminich Update to Gradle 3.1

Code Kata: Trading Card Game (TCG) Build Status

In this Code Kata you will be implementing a two-player trading card game. The rules are loosely based on Hearthstone - Heroes of Warcraft®. This Kata is supposed to be slightly more complex than some of the well-known traditional Katas (e.g. Roman Numbers, Bowling Game or FizzBuzz) especially when adding some of the Advanced Variations proposed below. Kata TCG leaves room for different focuses (like playing cards based on user input and/or algorithmic decision logic) and can be approached iteratively with TDD from different angles. The Kata should also be well suited for your own rule extensions and modifications. It should offer challenges for developers of all experience levels.

Kata TCG is now listed in the Kata Catalogue hosted at

TCG Rules


Each player starts the game with 30 Health and 0 Mana slots. Starting Health and Mana
Each player starts with a deck of 20 Damage cards with the following Mana costs: 0,0,1,1,2,2,2,3,3,3,3,4,4,4,5,5,6,6,7,8 Default Starting Deck
From the deck each player receives 3 random cards has his initial hand. Draw Starting Hand
One player is randomly chosen to be the starting active player. The other player draws a 4th card from his deck to compensate him for not playing the first turn. Starting Player and Extra Card

Basic Gameplay

Step Rule
1. The active player receives 1 Mana slot up to a maximum of 10 total slots. Receiving Mana Slot
2. The active player's empty Mana slots are refilled. Mana Refill
3. The active player draws a random card from his deck. Draw Card
4. The active player can play as many cards as he can afford. Any played card empties Mana slots and deals immediate damage to the opponent player equal to its Mana cost. Cause Damage
5. If the opponent player's Health drops to or below zero the active player wins the game. Kill Opponent
6. If the active player can't (by either having no cards left in his hand or lacking sufficient Mana to pay for any hand card) or simply doesn't want to play another card, the opponent player becomes active.

Special Rules

Rule Description
Bleeding Out If a player's card deck is empty before the game is over he receives 1 damage instead of drawing a card when it's his turn. Bleedout
Overload If a player draws a card that lets his hand size become >5 that card is discarded instead of being put into his hand. Overload
Dud Card The 0 Mana cards can be played for free but don't do any damage either. They are just annoyingly taking up space in your hand. Dud Card

Advanced Variations

When the normal game rules have become too easy/boring you might consider adding some additional rules like those described below. Some of them will increase the complexity of the game significantly, so you might not want to use all extra rules at once:


When playing a card the active player can choose to use it for causing damage (see Basic Gameplay) or for healing himself by a value equal to the mana cost amount. Healing
Players cannot heal up above 30 health. Health Cap


Let players choose to play cards either as immediate damage Attacks (same as cards generally worked in the Basic Gameplay rules) or as Minions that are put on the board instead. Minions will use the mana cost of their card as Health and Damage value. Playing a 0 card will create a minion with 1 Health and 0 Damage. Playing Card as Minion
Health has to be tracked when they receive damage.
Each player can have a maximum of 3 Minions on the board at any given time.
A Minion will sleep in the turn it was put on the board. Sleeping on first turn
In any subsequent turn each Minion can be used once to deal damage to the opponent player or an opponent Minion. Attacking Opponent or enemy Minion
A Minion fighting another Minion will result in them dealing their damage value to each other simultaneously. Simultaneous Damage
Sleeping Minions will defend themselves in the same way when attacked by another Minion. Sleeping Minions fight back
Players can choose to play an Attack against a Minion. The attacked Minion will not defend itself in this case, thus the attacking player receives no damage from it. Player fighting Minion
When a Minions health drops to or below zero it is removed from the board. Kill Minion


  • Let Mana cost and damage dealt be different from each other thus making cheap powerful, expensive mediocre or entirely useless cards possible. This can add a whole new layer of play strategy as some cards might not be desired to be ever played, but eventually have to in order to free your hand for better cards.
  • Introduce Card Drawer cards that cost Mana but don't do any damage. Instead they let you draw a given number of cards from your deck. Those cards can be used in the current turn or later on (just as if normally drawn at the beginning of the active player's turn).
  • Allow players to create their own decks of 20 cards from a larger Card Pool. Let those decks be saved to and loaded from disk before starting a game.

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