Movement-Based Combat System Implementation

Overview

Implemented a complete grid-based combat system with movement, positioning, and range-based attacks. The system transforms static combat into dynamic spatial warfare where agents must move into range before attacking.

Phase 1: Data Model Extensions ✅

1.1 Weapon.cs

Added: WeaponType enum (Melee, Ranged, Magic)
Added: _range field (int, default 1 for melee)
Impact: Weapons now declare their combat class and effective range

1.2 Monster.cs

Added: MonsterSize enum (Small, Medium, Large)
Added: _size field (default Medium)
Mapping:
- Small: 4 creatures per square
- Medium: 1 creature per square (1x1)
- Large: 1 creature in 4x4 squares
Impact: Monsters occupy different amounts of grid space

1.3 CharacterStats.cs

Added: GetMovementRange() method
Formula: Speed / 2 (minimum 1 square per turn)
Impact: Speed stat now determines both initiative and movement capability

1.4 Combatant.cs

Added: GridPosition property (Vector2Int)
Added: Size property (MonsterSize)
Added Methods:
- DistanceTo(Combatant) - Manhattan distance
- IsAdjacentTo(Combatant) - 1 square away check
- CanReachTarget(Combatant, Weapon) - Range validation
- GetFootprintSize() - Grid size based on monster size
- GetCreaturesPerSquare() - Stacking limit

Phase 2: Combat Infrastructure ✅

2.1 CombatAction.cs (NEW)

public enum ActionType { Move, Attack, UseItem, Defend, Pass }
public class CombatAction

Represents turn decisions
Holds actor, action type, targets (combatant/position/item)
Flexible constructors for different action types
Used by CombatResolver to make combat determinate

2.2 MovementValidator.cs (NEW)

Static utility class for all combat rules:

CanAttack() - Range validation (melee adjacency, ranged within range)
CanMoveTo() - Movement validation (in bounds, speed limit, grid valid)
IsAdjacentTo() - Melee range check (1 square away)
ManhattanDistance() - Distance calculation
GetDirectionTowards() - Direction for pathfinding
GetNextPositionTowards() - Single step toward target

2.3 CombatGrid.cs (NEW)

Core spatial management system:

Constructor: CombatGrid(Vector2Int gridSize, float cellSize)

Default: 11x7 grid
Tracks all occupancy per cell

Key Methods:

PlaceAllCombatants() - Agents left side, monsters right side
IsPositionValid() - Respects grid bounds and size rules
TryMoveCombatant() - Atomic move with validation
GetReachablePositions() - BFS pathfinding within movement range
PlaceCombatant() - Place individual combatant
RemoveCombatant() - Remove from grid (on death)
GridToWorldPosition() / WorldToGridPosition() - Coordinate conversion

Occupancy Rules:

Large (4x4): Cannot share any space
Medium (1x1): Needs empty cell
Small: Up to 4 per square (stacking)

Phase 3: Event System Extensions ✅

3.1 CombatEvent.cs

New Event Kinds:

MovementStart - Actor begins moving
MovementComplete - Actor finishes moving
OutOfRange - Attack failed (ranged/magic out of range)
TooFarForMelee - Attack failed (not adjacent)
TargetUnreachable - Movement failed

New Event Fields:

SourcePosition (Vector2Int) - Where movement started
TargetPosition (Vector2Int) - Destination or target location
MovementDistance (int) - Squares moved

Phase 4: Combat Resolver Refactor ✅

4.1 Core Flow Changes

Old: Pick target → Attack every turn New:

InitializeGrid() - Create 11x7 grid, place all combatants
SelectActions() - Each combatant decides Move/Attack/UseItem
ExecuteActions() - Process decisions in order

4.2 New Methods

`InitializeGrid()`

Creates CombatGrid with 11x7 cells
Places combatants (agents left, monsters right)

`SelectActions()`

Agents check health, use potions if <20% HP
Pick random enemy target
Decision logic:
- If target in weapon range → Attack action
- If out of range → Move action (toward target)
- If no weapon or can't move → Pass action

`ExecuteActions()`

Processes all actions in turn order
Dispatches to specific executors

`ExecuteMovement()`

Updates grid position
Emits MovementStart, MovementComplete events
Records source, destination, distance in events

`ExecuteAttack()`

Validates range BEFORE attacking
Melee: Must be adjacent (distance = 1)
Ranged/Magic: Must be ≤ weapon.Range
Emits OutOfRange/TooFarForMelee if validation fails
Only calls TakeSwing() if valid

`ExecuteUseItem()`

Agents can use consumables during their turn
Immediate health restoration

4.3 Combat Flow

Round starts
├─ SelectActions (all actors decide)
│  └─ Pick target
│     ├─ In range? → Attack
│     └─ Out of range? → Move
├─ ExecuteActions (process decisions)
│  ├─ Movement (all moves for round)
│  ├─ Attacks (validated against actual positions)
│  └─ Items (consumables used)
└─ Check win conditions

Phase 5: BattleArenaView Animation ✅

5.1 Slot Class Enhancement

Added: CurrentGridPos - Tracks position on grid

5.2 PlaceCombatants() Refactor

Old: Hard-coded team layout
New: Uses grid positions from Combatant objects
Respects actual CombatGrid placement

5.3 CreateSlot() Size Scaling

Small:  0.4f scale  (smaller creatures)
Medium: 0.58f scale (default, human-sized)
Large:  1.2f scale  (larger creatures)

5.4 Replay() Event Handling

New Event Handlers:

MovementStart - Brief pause (0.2s)
MovementComplete → Movement() animation
OutOfRange / TooFarForMelee → RangeFailure() animation
HealthPotionUsed → HealPotion() animation

5.5 New Animation Methods

`Movement(CombatEvent e)`

Animates combatant from source to target position
Updates CurrentGridPos
Smooth glide over 0.6 beats

`RangeFailure(int combatantId)`

Visual feedback: brief shake effect
3 cycles of left-right motion
Indicates attack couldn't connect

`HealPotion(CombatEvent e)`

Green color flash
Green floating text (+amount)
Updates displayed health
0.6s total animation

5.6 Position Tracking Updates

Strike(): Uses actual grid positions from events
ApplyFinalState(): Uses final combatant GridPosition
DrawNameplates(): Uses Transform.position (dynamic)
AddFloater(): Uses Transform.position (dynamic)

Architecture Integration 🔗

BattleArenaView (Animation)
    ↑
    │ replays events with positions
    │
CombatResolver (Logic)
    ├─ InitializeGrid() → CombatGrid
    ├─ SelectActions() → CombatAction[]
    ├─ ExecuteActions()
    │   ├─ ExecuteMovement() → uses MovementValidator
    │   ├─ ExecuteAttack() → uses MovementValidator
    │   └─ ExecuteUseItem()
    │
    └─ Emits CombatEvent[] (with positions)
        ├─ MovementStart
        ├─ MovementComplete
        ├─ OutOfRange
        ├─ TooFarForMelee
        ├─ TargetUnreachable
        ├─ Hit/Miss
        └─ Death
        
CombatGrid (Spatial State)
    ├─ PlaceAllCombatants()
    ├─ IsPositionValid()
    ├─ TryMoveCombatant()
    └─ GetReachablePositions()
        
MovementValidator (Rules)
    ├─ CanAttack()
    ├─ CanMoveTo()
    ├─ IsAdjacentTo()
    └─ ManhattanDistance()
        
Weapon (Type/Range)
    ├─ WeaponType enum
    └─ Range property

Monster (Size)
    └─ MonsterSize enum
    
Combatant (Positioning)
    ├─ GridPosition
    ├─ Size
    ├─ DistanceTo()
    ├─ CanReachTarget()
    └─ GetFootprintSize()

What This Enables ✨

✅ Spatial Combat - No more "attack from anywhere" ✅ Melee vs Ranged - Different weapons have different reach ✅ Speed-Based Movement - Faster = more squares per turn ✅ Smart AI - Agents automatically move into range ✅ Monster Sizes - Large/Medium/Small occupy different space ✅ Grid Stacking - Small creatures can stack (4 per square) ✅ Replayable Events - All movement recorded for animation ✅ Extensible - Easy to add Defend, Flee, abilities, etc.

Compatibility Notes ⚠️

Backwards Compatibility

Existing weapons default to Melee with Range=1 if not specified
Existing monsters default to MonsterSize.Medium
Agents default to MonsterSize.Medium
CombatResolver interface unchanged (still takes combatants, returns BattleResult)
CombatDirector calls unchanged

Testing Recommendations

Test melee combat (agent must be adjacent to monster)
Test ranged combat (agent moves into range, then attacks)
Test monster sizes:
- Small creatures stacking
- Large creatures blocking movement
- Medium creatures standard behavior
Test grid boundaries (combatants can't move off grid)
Test multiple combatants (ensure pathfinding avoids allies)
Test movement range calculation (Speed/2)
Test speed stat affecting both initiative and movement

Future Enhancements

Defend Action - Reduce incoming damage this turn
Ranged Abilities - Spells with area of effect
Terrain Effects - Obstacles, difficult terrain
Crowd Control - Stuns, roots, slows
Smart Pathfinding - Avoid allies, seek advantage
Flanking Mechanics - Bonuses for surrounding enemy
Line of Sight - Visibility-based targeting
Formations - Coordinated group movement

Performance Considerations

CombatGrid uses Dictionary for O(1) occupancy lookup
BFS pathfinding is O(n) where n = grid cells (77 for 11x7)
Movement validation is O(1) per cell
All spatial queries happen once per turn
No per-frame updates (resolved completely before animation)

Files Modified/Created

Modified

Weapon.cs - Added WeaponType, Range
Monster.cs - Added MonsterSize
CharacterStats.cs - Added GetMovementRange()
Combatant.cs - Added positioning and range methods
CombatEvent.cs - Added movement event kinds, position fields
CombatResolver.cs - Complete refactor with grid system
BattleArenaView.cs - Updated animation, position tracking

Created

CombatAction.cs - Action type system
CombatGrid.cs - Spatial grid management
MovementValidator.cs - Rule validation system

Total: 7 modified, 3 new = 10 files changed

Testing Checklist

Project compiles without errors
Basic fight resolves (agents vs monsters)
Melee attacks require adjacency
Ranged attacks work at range
Agents move into range automatically
Movement distance respects Speed stat
Large monsters block space
Small monsters stack (4 per square)
Health potions heal and show animation
Out of range attacks emit proper events
Movement animation plays correctly
Grid placement looks balanced
Final positions are accurate
Arena playback matches log-only mode

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