Initial Combat Implementation

Assets/_Project/Scripts/Server/Combat/HealthApplyDamageSystem.cs

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+using ProjectM.Simulation;
+using Unity.Burst;
+using Unity.Collections;
+using Unity.Entities;
+using Unity.Mathematics;
+using Unity.NetCode;
+
+namespace ProjectM.Server
+{
+    /// <summary>
+    /// Server-authoritative damage application. Drains each damageable entity's
+    /// <see cref="DamageEvent"/> buffer (appended by <see cref="ProjectileDamageSystem"/> earlier
+    /// this tick), subtracts the summed amount from <see cref="Health"/>, then clears the buffer so
+    /// each hit is applied exactly once. Entities that carry character stats (players) clamp to their
+    /// data-driven <see cref="EffectiveCharacterStats.MaxHealth"/> ceiling; others (training dummies)
+    /// clamp at zero. A dead <see cref="TrainingDummyTag"/> is destroyed; player death is deferred.
+    /// Health.Current is a <c>[GhostField]</c>, so the new value replicates to clients for display.
+    ///
+    /// Runs server-only (<see cref="WorldSystemFilterFlags.ServerSimulation"/>) inside the prediction
+    /// group so it shares tick timing with movement/damage, where it executes once per tick. The
+    /// single structural change (destroying a dead dummy) is batched through a frame-allocator
+    /// <see cref="EntityCommandBuffer"/> that is played back immediately to the entity manager — so a
+    /// plain-world EditMode test needs no separate ECB system.
+    /// </summary>
+    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
+    [UpdateInGroup(typeof(PredictedSimulationSystemGroup))]
+    [UpdateAfter(typeof(ProjectileDamageSystem))]
+    [BurstCompile]
+    public partial struct HealthApplyDamageSystem : ISystem
+    {
+        [BurstCompile]
+        public void OnUpdate(ref SystemState state)
+        {
+            var ecb = new EntityCommandBuffer(Allocator.Temp);
+
+            foreach (var (health, dmg, entity) in
+                     SystemAPI.Query<RefRW<Health>, DynamicBuffer<DamageEvent>>()
+                         .WithEntityAccess())
+            {
+                if (dmg.Length == 0)
+                    continue;
+
+                float total = 0f;
+                for (int i = 0; i < dmg.Length; i++)
+                    total += dmg[i].Amount;
+                dmg.Clear();
+
+                float newHp = health.ValueRO.Current - total;
+
+                // Effective max health (base + modifiers) is the runtime ceiling for entities that carry
+                // character stats (players); others just clamp at zero. No auto-heal on a max increase.
+                if (SystemAPI.HasComponent<EffectiveCharacterStats>(entity))
+                    newHp = math.clamp(newHp, 0f, SystemAPI.GetComponent<EffectiveCharacterStats>(entity).MaxHealth);
+                else
+                    newHp = math.max(0f, newHp);
+
+                health.ValueRW.Current = newHp;
+
+                // Server-authoritative death: training dummies despawn; player death is deferred (clamp only).
+                if (health.ValueRO.Current <= 0f && SystemAPI.HasComponent<TrainingDummyTag>(entity))
+                    ecb.DestroyEntity(entity);
+            }
+
+            ecb.Playback(state.EntityManager);
+            ecb.Dispose();
+        }
+    }
+}

Assets/_Project/Scripts/Server/Combat/HealthApplyDamageSystem.cs.meta

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+fileFormatVersion: 2
+guid: 7c1729291515a4966b83ef050554a772

Assets/_Project/Scripts/Server/Combat/ProjectileDamageSystem.cs

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+using ProjectM.Simulation;
+using Unity.Burst;
+using Unity.Collections;
+using Unity.Entities;
+using Unity.Mathematics;
+using Unity.NetCode;
+using Unity.Transforms;
+
+namespace ProjectM.Server
+{
+    /// <summary>
+    /// Server-authoritative projectile resolution: applies hits to damageable entities and expires
+    /// projectiles past their range. Runs in the server world only
+    /// (<see cref="WorldSystemFilterFlags.ServerSimulation"/>) inside the
+    /// <see cref="PredictedSimulationSystemGroup"/>, ordered <see cref="ProjectileMoveSystem"/> so the
+    /// projectile's <see cref="LocalTransform"/> is the post-move position for this tick.
+    ///
+    /// Hit detection is a <b>swept</b> planar (XZ) test: rather than checking the projectile's point
+    /// position (which tunnels straight through a target when the per-tick step exceeds the target's
+    /// radius — e.g. a fast projectile, or any projectile while the server is tick-batching under load),
+    /// it reconstructs the segment the projectile traversed this tick
+    /// (<c>[curPos - dir*speed*dt, curPos]</c>) and tests each target's hit radius against the closest
+    /// point on that segment. The target hit earliest along the path (smallest segment parameter) wins.
+    /// A target whose <see cref="GhostOwner"/> matches the projectile's owner is skipped (no self-hits);
+    /// dummies carry no <see cref="GhostOwner"/> and are therefore always valid targets.
+    ///
+    /// On a hit the system appends a <see cref="DamageEvent"/> to the target (consumed by
+    /// <c>HealthApplyDamageSystem</c>) and destroys the projectile. Deferring damage to a buffer lets a
+    /// single tick stack hits from multiple projectiles. All structural changes go through an
+    /// <see cref="EntityCommandBuffer"/> that plays back immediately to the
+    /// <see cref="EntityManager"/> (Temp allocator) — keeping this server-only, once-per-tick system
+    /// self-contained and plain-world testable without a separate ECB system.
+    /// </summary>
+    [BurstCompile]
+    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
+    [UpdateInGroup(typeof(PredictedSimulationSystemGroup))]
+    [UpdateAfter(typeof(ProjectileMoveSystem))]
+    public partial struct ProjectileDamageSystem : ISystem
+    {
+        /// <summary>Lookup used to read a target's owner so a projectile never hits its own caster.</summary>
+        ComponentLookup<GhostOwner> m_GhostOwnerLookup;
+
+        /// <summary>Extra forgiveness added to a target's hit radius to approximate the projectile's own size.</summary>
+        const float k_ProjectileRadius = 0.2f;
+
+        [BurstCompile]
+        public void OnCreate(ref SystemState state)
+        {
+            m_GhostOwnerLookup = state.GetComponentLookup<GhostOwner>(isReadOnly: true);
+
+            // No projectiles → nothing to expire or hit-test; skip the tick (and its allocations) entirely.
+            state.RequireForUpdate<Projectile>();
+        }
+
+        [BurstCompile]
+        public void OnUpdate(ref SystemState state)
+        {
+            m_GhostOwnerLookup.Update(ref state);
+
+            float dt = SystemAPI.Time.DeltaTime;
+            var ecb = new EntityCommandBuffer(Allocator.Temp);
+
+            // Snapshot all damageable targets once for this tick. Stable iteration order (query order).
+            var targetEntities = new NativeList<Entity>(Allocator.Temp);
+            var targetPositions = new NativeList<float3>(Allocator.Temp);
+            var targetRadii = new NativeList<float>(Allocator.Temp);
+
+            foreach (var (xform, hitRadius, targetEntity) in
+                     SystemAPI.Query<RefRO<LocalTransform>, RefRO<HitRadius>>()
+                         .WithAll<Health>()
+                         .WithEntityAccess())
+            {
+                targetEntities.Add(targetEntity);
+                targetPositions.Add(xform.ValueRO.Position);
+                targetRadii.Add(hitRadius.ValueRO.Value);
+            }
+
+            foreach (var (xform, proj, owner, projectileEntity) in
+                     SystemAPI.Query<RefRO<LocalTransform>, RefRO<Projectile>, RefRO<GhostOwner>>()
+                         .WithEntityAccess())
+            {
+                int projOwnerId = owner.ValueRO.NetworkId;
+
+                // This tick's planar travel segment: [segStart -> segEnd]. Sweeping the segment (rather
+                // than testing only segEnd) is what prevents fast projectiles from tunnelling targets.
+                float3 cur = xform.ValueRO.Position;
+                float2 segEnd = new float2(cur.x, cur.z);
+                float2 segStart = segEnd - proj.ValueRO.Direction * (proj.ValueRO.Speed * dt);
+                float2 seg = segEnd - segStart;
+                float segLenSq = math.lengthsq(seg);
+
+                int bestIdx = -1;
+                float bestT = float.MaxValue;
+                for (int i = 0; i < targetEntities.Length; i++)
+                {
+                    var target = targetEntities[i];
+
+                    // Skip the caster: a target whose GhostOwner matches the projectile owner is the
+                    // shooter (or another ghost they own). Dummies have no GhostOwner, so never skipped.
+                    if (m_GhostOwnerLookup.HasComponent(target) &&
+                        m_GhostOwnerLookup[target].NetworkId == projOwnerId)
+                        continue;
+
+                    float2 tp = new float2(targetPositions[i].x, targetPositions[i].z);
+
+                    // Closest point on the travel segment to the target centre.
+                    float t = segLenSq > 1e-8f
+                        ? math.saturate(math.dot(tp - segStart, seg) / segLenSq)
+                        : 0f;
+                    float2 closest = segStart + t * seg;
+
+                    float hitDist = targetRadii[i] + k_ProjectileRadius;
+                    if (math.distancesq(tp, closest) <= hitDist * hitDist && t < bestT)
+                    {
+                        bestT = t;
+                        bestIdx = i;
+                    }
+                }
+
+                if (bestIdx >= 0)
+                {
+                    // Earliest target along the travel path: deal damage and consume the projectile.
+                    ecb.AppendToBuffer(targetEntities[bestIdx], new DamageEvent
+                    {
+                        Amount = proj.ValueRO.Damage,
+                        SourceNetworkId = projOwnerId,
+                    });
+                    ecb.DestroyEntity(projectileEntity);
+                    continue;
+                }
+
+                // Nothing hit this tick: expire the projectile once it has travelled its full range.
+                if (proj.ValueRO.DistanceTravelled >= proj.ValueRO.Range)
+                    ecb.DestroyEntity(projectileEntity);
+            }
+
+            ecb.Playback(state.EntityManager);
+
+            ecb.Dispose();
+            targetEntities.Dispose();
+            targetPositions.Dispose();
+            targetRadii.Dispose();
+        }
+    }
+}

Assets/_Project/Scripts/Server/Combat/ProjectileDamageSystem.cs.meta

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+fileFormatVersion: 2
+guid: f19fa77609fa04c2ca4e293f19c052a4

Assets/_Project/Scripts/Server/Combat/TrainingDummySpawnSystem.cs

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+using ProjectM.Simulation;
+using Unity.Burst;
+using Unity.Collections;
+using Unity.Entities;
+using Unity.Mathematics;
+using Unity.Transforms;
+
+namespace ProjectM.Server
+{
+    /// <summary>
+    /// Server-only, one-shot dummy spawner. On its first update it reads the baked
+    /// <see cref="TrainingDummySpawner"/> singleton and instantiates <c>Count</c> training-dummy
+    /// ghosts in a row, spaced <c>Spacing</c> world-units apart along +X starting at <c>Origin</c>.
+    /// It then destroys the spawner singleton entity so <c>RequireForUpdate<TrainingDummySpawner></c>
+    /// is no longer satisfied and the system stops running (idempotent: dummies are spawned exactly once).
+    /// Runs in the default <see cref="SimulationSystemGroup"/> (NOT the prediction loop) since spawning is
+    /// a non-predicted, server-authoritative event; the dummies replicate to clients as interpolated ghosts.
+    /// All structural changes are batched through an <see cref="EntityCommandBuffer"/>.
+    /// </summary>
+    [BurstCompile]
+    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
+    public partial struct TrainingDummySpawnSystem : ISystem
+    {
+        [BurstCompile]
+        public void OnCreate(ref SystemState state)
+        {
+            state.RequireForUpdate<TrainingDummySpawner>();
+        }
+
+        [BurstCompile]
+        public void OnUpdate(ref SystemState state)
+        {
+            // Grab both the singleton entity (to destroy when done) and its baked config.
+            var spawnerEntity = SystemAPI.GetSingletonEntity<TrainingDummySpawner>();
+            var spawner = SystemAPI.GetComponent<TrainingDummySpawner>(spawnerEntity);
+
+            var ecb = new EntityCommandBuffer(Allocator.Temp);
+
+            for (int i = 0; i < spawner.Count; i++)
+            {
+                var dummy = ecb.Instantiate(spawner.Prefab);
+                var position = spawner.Origin + new float3(i * spawner.Spacing, 0f, 0f);
+                ecb.SetComponent(dummy, LocalTransform.FromPosition(position));
+            }
+
+            // One-shot: remove the spawner so RequireForUpdate fails and the system idles.
+            ecb.DestroyEntity(spawnerEntity);
+
+            ecb.Playback(state.EntityManager);
+        }
+    }
+}

Assets/_Project/Scripts/Server/Combat/TrainingDummySpawnSystem.cs.meta

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+fileFormatVersion: 2
+guid: 7673acbc74f7a4bddbca0679122511ea

Assets/_Project/Scripts/Server/Combat/UpgradePickupSpawnSystem.cs

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+using ProjectM.Simulation;
+using Unity.Burst;
+using Unity.Collections;
+using Unity.Entities;
+using Unity.Mathematics;
+using Unity.Transforms;
+
+namespace ProjectM.Server
+{
+    /// <summary>
+    /// Server-only, one-shot upgrade-pickup spawner (mirrors TrainingDummySpawnSystem). On its first
+    /// update it reads the baked <see cref="UpgradePickupSpawner"/> singleton and instantiates
+    /// <c>Count</c> pickup ghosts in a row, spaced <c>Spacing</c> world-units apart along +X starting at
+    /// <c>Origin</c>, then destroys the singleton so the system idles (spawned exactly once). Runs in the
+    /// default <see cref="SimulationSystemGroup"/> (NOT the prediction loop); pickups replicate to clients
+    /// as interpolated ghosts. Structural changes are batched through an <see cref="EntityCommandBuffer"/>.
+    /// </summary>
+    [BurstCompile]
+    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
+    public partial struct UpgradePickupSpawnSystem : ISystem
+    {
+        [BurstCompile]
+        public void OnCreate(ref SystemState state)
+        {
+            state.RequireForUpdate<UpgradePickupSpawner>();
+        }
+
+        [BurstCompile]
+        public void OnUpdate(ref SystemState state)
+        {
+            var spawnerEntity = SystemAPI.GetSingletonEntity<UpgradePickupSpawner>();
+            var spawner = SystemAPI.GetComponent<UpgradePickupSpawner>(spawnerEntity);
+
+            var ecb = new EntityCommandBuffer(Allocator.Temp);
+
+            if (spawner.Prefab != Entity.Null)
+            {
+                for (int i = 0; i < spawner.Count; i++)
+                {
+                    var pickup = ecb.Instantiate(spawner.Prefab);
+                    var position = spawner.Origin + new float3(i * spawner.Spacing, 0f, 0f);
+                    ecb.SetComponent(pickup, LocalTransform.FromPosition(position));
+                }
+            }
+
+            // One-shot: remove the spawner so RequireForUpdate fails and the system idles.
+            ecb.DestroyEntity(spawnerEntity);
+
+            ecb.Playback(state.EntityManager);
+        }
+    }
+}

Assets/_Project/Scripts/Server/Combat/UpgradePickupSpawnSystem.cs.meta

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+fileFormatVersion: 2
+guid: 602544c80ca5649258a9d6ca9ad74f79

Assets/_Project/Scripts/Server/Combat/UpgradePickupSystem.cs

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+using ProjectM.Simulation;
+using Unity.Burst;
+using Unity.Collections;
+using Unity.Entities;
+using Unity.Mathematics;
+using Unity.Transforms;
+
+namespace ProjectM.Server
+{
+    /// <summary>
+    /// Server-authoritative upgrade pickup grant. When a player overlaps an <see cref="UpgradePickup"/>
+    /// (planar XZ distance within the pickup's <see cref="HitRadius"/>), appends the pickup's modifier to
+    /// the player's replicated <see cref="StatModifier"/> buffer (which replicates to the predicting
+    /// owner, so StatRecomputeSystem folds identical effective stats on both worlds) and destroys the
+    /// pickup. Runs in the default <see cref="SimulationSystemGroup"/> (NOT the prediction loop) since the
+    /// grant is a non-predicted server event. The buffer append + pickup destroy are batched through an
+    /// <see cref="EntityCommandBuffer"/> played back immediately — so a plain-world EditMode test needs no
+    /// separate ECB system.
+    /// </summary>
+    [BurstCompile]
+    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
+    public partial struct UpgradePickupSystem : ISystem
+    {
+        [BurstCompile]
+        public void OnCreate(ref SystemState state)
+        {
+            state.RequireForUpdate<UpgradePickup>();
+        }
+
+        [BurstCompile]
+        public void OnUpdate(ref SystemState state)
+        {
+            // Snapshot modifiable players (carrying the modifier buffer + a transform) once this tick.
+            var playerEntities = new NativeList<Entity>(Allocator.Temp);
+            var playerPositions = new NativeList<float3>(Allocator.Temp);
+            foreach (var (xform, e) in
+                     SystemAPI.Query<RefRO<LocalTransform>>()
+                         .WithAll<PlayerTag, StatModifier>()
+                         .WithEntityAccess())
+            {
+                playerEntities.Add(e);
+                playerPositions.Add(xform.ValueRO.Position);
+            }
+
+            var ecb = new EntityCommandBuffer(Allocator.Temp);
+
+            foreach (var (xform, radius, pickup, pickupEntity) in
+                     SystemAPI.Query<RefRO<LocalTransform>, RefRO<HitRadius>, RefRO<UpgradePickup>>()
+                         .WithEntityAccess())
+            {
+                float2 pp = new float2(xform.ValueRO.Position.x, xform.ValueRO.Position.z);
+                float r = radius.ValueRO.Value;
+
+                for (int i = 0; i < playerEntities.Length; i++)
+                {
+                    float2 cp = new float2(playerPositions[i].x, playerPositions[i].z);
+                    if (math.distancesq(pp, cp) > r * r)
+                        continue;
+
+                    ecb.AppendToBuffer(playerEntities[i], new StatModifier
+                    {
+                        Target = pickup.ValueRO.Target,
+                        Op = pickup.ValueRO.Op,
+                        Value = pickup.ValueRO.Value,
+                        SourceId = pickup.ValueRO.SourceId,
+                    });
+                    ecb.DestroyEntity(pickupEntity);
+                    break; // granted to the first overlapping player, then despawns
+                }
+            }
+
+            ecb.Playback(state.EntityManager);
+            ecb.Dispose();
+            playerEntities.Dispose();
+            playerPositions.Dispose();
+        }
+    }
+}

Assets/_Project/Scripts/Server/Combat/UpgradePickupSystem.cs.meta

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+fileFormatVersion: 2
+guid: c3d9ef25fbc464e52aa342b531d6f35e