If you're building a Digital TCG or CCG, a deck-building roguelike or any turn-based card battler in Godot, you've probably noticed the pattern: the popular card addons give you beautiful hands, drag-and-drop and pile management — and then you're on your own for turns, mana, combat math and AI.

Card Combat Engine is that missing part. It is a logic-only engine (no rendering, no scenes required) that runs the entire battle:

• A turn state machine (BEGIN → PREPARATION → MAIN → ATTACK → DEFENSE → RESOLVE → END) you drive from your UI — or auto-resolve headlessly.
• Decks with hand / draw pile / board / graveyard, per-side mana pools, and fully generic extra zones (exile, banished, extra deck…).
• Creatures, spells (damage / heal / buff / AoE / summon), auras, persistent enchantments, and multi-target or hero-targeted effects.
• Attack/defense/block declaration with simultaneous damage resolution.
• Multi-side combat out of the box: 1v1, free-for-all, 2v2 with teams.

Domain-agnostic by design. The engine knows nothing about your GDD. Card taxonomy, rarities and ability semantics live in opaque containers (CardData.metadata) and 14 Callable injection points (ability_fn, damage_fn, cost_fn, attack_restriction_fn…). An optional AbilityLibrary ships 14 ready-made keywords — CHARGE, IMMUNITY, TAUNT, LIFESTEAL, THORNS, STEALTH, WINDFURY, FREEZE, ARMOR, BATTLECRY, SPELLPOWER, LORD, OVERKILL, SPELLBURST — that you can adopt, fork or ignore.

Deterministic and multiplayer-ready. Shuffles and AI are seeded: the same seed replays the same combat bit-for-bit. A command log gives you replay-from-input; full serialization gives you save/resume mid-combat. Run thousands of headless simulations for balancing, or put the engine on a server for authoritative netcode.

Engineered, not improvised. 418 GUT unit tests, a 4-stage CI pipeline (compile gate, unit tests, leak gate, lint gate), no autoloads, no editor tooling — copy addons/card_combat/ into your project and classes register via class_name.

Pick your license. AGPLv3 for open projects, or a one-time commercial license to ship closed-source and run server-side without copyleft obligations. Both packages contain byte-identical code.

Includes a runnable demo, an integration guide and a step-by-step tutorial.

• Complete battle loop — turn FSM, mana ramp, draw, attack/defense/block, simultaneous damage resolution
• Logic only, zero UI — pairs with any presentation addon (e.g. chun92's Card Framework) or your own scenes
• Deterministic by seed — bit-for-bit replays, balancing sims, server-authoritative multiplayer
• 14 injection points — abilities, damage formulas, costs, targeting rules: your game logic, never engine forks
• 14 keyword abilities included — optional AbilityLibrary with TAUNT, LIFESTEAL, BATTLECRY, OVERKILL and more
• 1v1, FFA and 2v2 — N-sided combat topology with team support, plus save/resume serialization
• 418 unit tests + 4-stage CI — compile, unit, leak and lint gates on every commit