mtg-online-drafter/docs/development/devlog/2024-12-18-200000_engine_enhancements.md

Strict Engine Enhancements: Layers, Tokens, Mulligan

Status: Completed

Objectives

• Implement Basic Layer System for continuous effects (P/T modifications).
• Implement Token Creation mechanism.
• Implement Mulligan System (London Rule).
• Update Game Lifecycle to include Setup/Mulligan phase.

Logic Overview

Layer System (RulesEngine.recalculateLayers)

• Implements Layer 7 (Power/Toughness) basics:
  • Layer 7b: Set P/T (set_pt).
  • Layer 7c: Modify P/T (pt_boost).
  • Layer 7d: Counters (+1/+1, -1/-1).
• recalculateLayers is called automatically whenever priority resets or actions occur.
• Modifiers with untilEndOfTurn: true are automatically cleared in the cleanup step.

Token Creation

• New action CREATE_TOKEN added.
• createToken method constructs a CardObject on the battlefield with defined stats.
• Triggers layer recalculation immediately.

Mulligan System

• New Phase: setup, New Step: mulligan.
• Game starts in setup/mulligan.
• Logic:
  • If a player has 0 cards and hasn't kept, they draw 7 automatically.
  • Action MULLIGAN_DECISION:
    • keep: false -> Shuffles hand into library, draws 7, increments mulliganCount.
    • keep: true -> Validates cardsToBottom count matches mulliganCount. Moves excess cards to library. Sets handKept = true.
• When all players keep, the engine automatically advances to beginning/untap.
• Supports London Mulligan rule (Draw 7, put X on bottom).

Technical Changes

• Updated StrictGameState and PlayerState types.
• Updated GameManager initialization and action switching.
• Updated RulesEngine transition logic.

Remaining/Next

• Frontend UI for Mulligan (Needs a Modal to Keep/Mull).
• Frontend UI for "Cards to Bottom" selection if X > 0.
• Frontend UI to visualize Tokens.