Make a Deckbuilding Battle: Energy, Block and Discard Piles

What you will build

Win one encounter using Strike, Guard, energy and visible intent.

1. Extract into a new folder and run node check.mjs from that folder.
2. For the browser games, run python3 -m http.server 8080 with Python 3 and open http://localhost:8080/index.html. Do not open modules with file://.
3. Read the full setup instructions and the original code licence. Keep your existing game on a separate test branch.

The JavaScript behaviour checks and native C comparison can run independently of the browser. Ghidra UI, physical-phone and your engine integration are separate checks. This is a small reference, not a certification of your project.

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Five practical steps

1. Make one deterministic encounter

   Start Deck battler. The player has eighteen health and three energy; the enemy has eighteen health and announces seven damage. Strike deals six; Guard adds five block. These small numbers let you calculate a turn before playing it.

   Expected result: A visible hand, energy count and enemy intent.

   Check it: Confirm the initial hand is Strike, Guard, Strike and every card costs one energy.

   playObserve the inputs → check the state → compare the result

2. Own card play in one function

   deck.play validates a current hand index, energy and active encounter before removing the card. Apply its effect, spend energy and put it in discard. Render from the resulting hand so removed-card indices do not refer to yesterday’s UI.

   Expected result: A card leaves the hand exactly once and spends one energy.

   Check it: Click an invalid index or play with zero energy; health, hand and piles stay unchanged.

3. Resolve the enemy turn explicitly

   End turn applies max(0,7-block) damage, clears block, discards the unused hand and refills energy. Draw up to three cards, refilling the draw pile from discard when empty. This reference uses a fixed order to support repeatable tests; it is not a random shuffle.

   Expected result: No negative damage, persistent old block or unlimited hand.

   Check it: Play Guard, then end turn: take two damage and start the next turn with zero block.

4. Stop combat immediately at an outcome

   A lethal Strike ends combat before the enemy can retaliate. A lethal enemy turn also ends the encounter. Every later play/end-turn action rejects the finished state. Restart creates new piles instead of reusing an old hand.

   Expected result: A win or loss that cannot keep mutating in the background.

   Check it: Win with three total strikes; repeatedly press End turn and confirm health and piles remain unchanged.

5. Extend toward a deckbuilder

   This is a battle recipe, not a complete roguelike. Add one post-win card reward and a second encounter before a map, shop or hundreds of cards. If you add shuffle, inject a seeded random source and preserve the deterministic test path.

   Expected result: A small original two-battle run with bounded card rules.

   Check it: Test empty piles, duplicate cards, restart, touch controls and save schema before adding persistent runs.

Read and reuse the actual code

deck.mjs: complete source · Standalone behavioural checks · Shared browser runner and input. Original BINX Forge code, MIT; the package includes every required file and its notice.

export function create(){return {hp:18,enemy:18,energy:3,block:0,turn:1,hand:['strike','guard','strike'],discard:[],draw:['guard','strike','guard'],ended:false,won:false};}
const refill=s=>{while(s.hand.length<3){if(!s.draw.length)s.draw=s.discard.splice(0);if(!s.draw.length)break;s.hand.push(s.draw.shift());}};
export function play(s,index){if(s.ended||s.energy<1||!Number.isInteger(index)||index<0||index>=s.hand.length)return false;const c=s.hand.splice(index,1)[0];s.energy--;if(c==='strike')s.enemy=Math.max(0,s.enemy-6);else s.block+=5;s.discard.push(c);if(!s.enemy){s.ended=true;s.won=true;}return true;}
export function endTurn(s){if(s.ended)return false;s.hp=Math.max(0,s.hp-Math.max(0,7-s.block));s.block=0;s.discard.push(...s.hand.splice(0));s.energy=3;s.turn++;refill(s);if(!s.hp){s.ended=true;s.won=false;}return true;}

Code rights: the included MIT notice permits use, modification and distribution, including commercial games and source products, with the copyright and licence notice. Added third-party files have their own terms. Read the official licence & usage terms.

Common failures and fixes

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Change one system after the baseline works. Keep the free reference and compare the same inputs before and after.

Optional building blocks from original creators

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Godot

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Kenney

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Interface artwork for buttons, panels and sliders.

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Inspect exact formats and editions on each resource page. Pay for a resource only when it fills an identified gap; the free code exercise needs no paid engine or pack.

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