Part 13

Source/Engine/Door.swift

@@ -72,6 +72,7 @@ public extension Door {
         case .closed:
             if world.player.intersection(with: self) != nil {
                 state = .opening
+                world.playSound(.doorSlide, at: position)
                 time = 0
             }
         case .opening:
@@ -82,6 +83,7 @@ public extension Door {
         case .open:
             if time >= closeDelay {
                 state = .closing
+                world.playSound(.doorSlide, at: position)
                 time = 0
             }
         case .closing:

Source/Engine/Monster.swift

@@ -41,6 +41,7 @@ public extension Monster {
             if canSeePlayer(in: world) {
                 state = .chasing
                 animation = .monsterWalk
+                world.playSound(.monsterGroan, at: position)
             }
         case .chasing:
             guard canSeePlayer(in: world) else {
@@ -67,11 +68,12 @@ public extension Monster {
             if animation.time - lastAttackTime >= attackCooldown {
                 lastAttackTime = animation.time
                 world.hurtPlayer(10)
+                world.playSound(.monsterSwipe, at: position)
             }
         case .hurt:
             if animation.isCompleted {
-                state = .idle
-                animation = .monsterIdle
+                state = .chasing
+                animation = .monsterWalk
             }
         case .dead:
             if animation.isCompleted {

Source/Engine/Player.swift

@@ -22,12 +22,14 @@ public struct Player: Actor {
     public var state: PlayerState = .idle
     public var animation: Animation = .pistolIdle
     public let attackCooldown: Double = 0.25
+    public let soundChannel: Int
 
-    public init(position: Vector) {
+    public init(position: Vector, soundChannel: Int) {
         self.position = position
         self.velocity = Vector(x: 0, y: 0)
         self.direction = Vector(x: 1, y: 0)
         self.health = 100
+        self.soundChannel = soundChannel
     }
 }
 
@@ -36,6 +38,10 @@ public extension Player {
         return health <= 0
     }
 
+    var isMoving: Bool {
+        return velocity.x != 0 || velocity.y != 0
+    }
+
     var canFire: Bool {
         switch state {
         case .idle:
@@ -46,14 +52,20 @@ public extension Player {
     }
 
     mutating func update(with input: Input, in world: inout World) {
+        let wasMoving = isMoving
         direction = direction.rotated(by: input.rotation)
         velocity = direction * input.speed * speed
         if input.isFiring, canFire {
             state = .firing
             animation = .pistolFire
+            world.playSound(.pistolFire, at: position)
             let ray = Ray(origin: position, direction: direction)
             if let index = world.pickMonster(ray) {
                 world.hurtMonster(at: index, damage: 10)
+                world.playSound(.monsterHit, at: world.monsters[index].position)
+            } else {
+                let position = world.hitTest(ray)
+                world.playSound(.ricochet, at: position)
             }
         }
         switch state {
@@ -65,6 +77,11 @@ public extension Player {
                 animation = .pistolIdle
             }
         }
+        if isMoving, !wasMoving {
+            world.playSound(.playerWalk, at: position, in: soundChannel)
+        } else if !isMoving {
+            world.playSound(nil, at: position, in: soundChannel)
+        }
     }
 }
 

Source/Engine/Pushwall.swift

@@ -12,11 +12,13 @@ public struct Pushwall: Actor {
     public var position: Vector
     public var velocity: Vector
     public let tile: Tile
+    public let soundChannel: Int
 
-    public init(position: Vector, tile: Tile) {
+    public init(position: Vector, tile: Tile, soundChannel: Int) {
         self.position = position
         self.velocity = Vector(x: 0, y: 0)
         self.tile = tile
+        self.soundChannel = soundChannel
     }
 }
 
@@ -45,6 +47,7 @@ public extension Pushwall {
     }
 
     mutating func update(in world: inout World) {
+        let wasMoving = isMoving
         if isMoving == false, let intersection = world.player.intersection(with: self) {
             if abs(intersection.x) > abs(intersection.y) {
                 velocity = Vector(x: intersection.x > 0 ? speed : -speed, y: 0)
@@ -58,5 +61,13 @@ public extension Pushwall {
             position.x = position.x.rounded(.down) + 0.5
             position.y = position.y.rounded(.down) + 0.5
         }
+        if isMoving {
+            world.playSound(.wallSlide, at: position, in: soundChannel)
+        } else if !isMoving {
+            world.playSound(nil, at: position, in: soundChannel)
+            if wasMoving {
+                world.playSound(.wallThud, at: position)
+            }
+        }
     }
 }

Source/Engine/Sounds.swift

@@ -0,0 +1,31 @@
+//
+//  Sounds.swift
+//  Engine
+//
+//  Created by Nick Lockwood on 11/11/2019.
+//  Copyright © 2019 Nick Lockwood. All rights reserved.
+//
+
+public enum SoundName: String, CaseIterable {
+    case pistolFire
+    case ricochet
+    case monsterHit
+    case monsterGroan
+    case monsterDeath
+    case monsterSwipe
+    case doorSlide
+    case wallSlide
+    case wallThud
+    case switchFlip
+    case playerDeath
+    case playerWalk
+    case squelch
+}
+
+public struct Sound {
+    public let name: SoundName?
+    public let channel: Int?
+    public let volume: Double
+    public let pan: Double
+    public let delay: Double
+}

Source/Engine/Switch.swift

@@ -35,6 +35,7 @@ public extension Switch {
             if world.player.rect.intersection(with: self.rect) != nil {
                 state = .on
                 animation = .switchFlip
+                world.playSound(.switchFlip, at: position)
             }
         case .on:
             if animation.isCompleted {

Source/Engine/World.swift

@@ -8,6 +8,7 @@
 
 public enum WorldAction {
     case loadLevel(Int)
+    case playSounds([Sound])
 }
 
 public struct World {
@@ -19,6 +20,7 @@ public struct World {
     public private(set) var player: Player!
     public private(set) var effects: [Effect]
     public private(set) var isLevelEnded: Bool
+    private var sounds: [Sound] = []
 
     public init(map: Tilemap) {
         self.map = map
@@ -130,7 +132,9 @@ public extension World {
             hurtMonster(at: i, damage: 1)
         }
 
-        return nil
+        // Play sounds
+        defer { sounds.removeAll() }
+        return .playSounds(sounds)
     }
 
     var sprites: [Billboard] {
@@ -149,6 +153,10 @@ public extension World {
         effects.append(Effect(type: .fadeIn, color: color, duration: 0.2))
         if player.isDead {
             effects.append(Effect(type: .fizzleOut, color: .red, duration: 2))
+            playSound(.playerDeath, at: player.position)
+            if player.isStuck(in: self) {
+                playSound(.squelch, at: player.position)
+            }
         }
     }
 
@@ -162,13 +170,34 @@ public extension World {
         if monster.isDead {
             monster.state = .dead
             monster.animation = .monsterDeath
+            playSound(.monsterDeath, at: monster.position)
+            if monster.isStuck(in: self) {
+                playSound(.squelch, at: monster.position)
+            }
         } else {
             monster.state = .hurt
             monster.animation = .monsterHurt
         }
         monsters[index] = monster
     }
 
+    mutating func playSound(_ name: SoundName?, at position: Vector, in channel: Int? = nil) {
+        let delta = position - player.position
+        let distance = delta.length
+        let dropOff = 0.5
+        let volume = 1 / (distance * distance * dropOff + 1)
+        let delay = distance * 2 / 343
+        let direction = distance > 0 ? delta / distance : player.direction
+        let pan = player.direction.orthogonal.dot(direction)
+        sounds.append(Sound(
+            name: name,
+            channel: channel,
+            volume: volume,
+            pan: pan,
+            delay: delay
+        ))
+    }
+
     mutating func endLevel() {
         isLevelEnded = true
         effects.append(Effect(type: .fadeOut, color: .black, duration: 2))
@@ -186,6 +215,7 @@ public extension World {
         self.switches = []
         self.isLevelEnded = false
         var pushwallCount = 0
+        var soundChannel = 0
         for y in 0 ..< map.height {
             for x in 0 ..< map.width {
                 let position = Vector(x: Double(x) + 0.5, y: Double(y) + 0.5)
@@ -194,7 +224,8 @@ public extension World {
                 case .nothing:
                     break
                 case .player:
-                    self.player = Player(position: position)
+                    self.player = Player(position: position, soundChannel: soundChannel)
+                    soundChannel += 1
                 case .monster:
                     monsters.append(Monster(position: position))
                 case .door:
@@ -205,7 +236,12 @@ public extension World {
                     pushwallCount += 1
                     if pushwalls.count >= pushwallCount {
                         let tile = pushwalls[pushwallCount - 1].tile
-                        pushwalls[pushwallCount - 1] = Pushwall(position: position, tile: tile)
+                        pushwalls[pushwallCount - 1] = Pushwall(
+                            position: position,
+                            tile: tile,
+                            soundChannel: soundChannel
+                        )
+                        soundChannel += 1
                         break
                     }
                     var tile = map[x, y]
@@ -214,7 +250,12 @@ public extension World {
                     } else {
                         tile = map.closestFloorTile(to: x, y) ?? .wall
                     }
-                    pushwalls.append(Pushwall(position: position, tile: tile))
+                    pushwalls.append(Pushwall(
+                        position: position,
+                        tile: tile,
+                        soundChannel: soundChannel
+                    ))
+                    soundChannel += 1
                 case .switch:
                     precondition(map[x, y].isWall, "Switch must be placed on a wall tile")
                     switches.append(Switch(position: position))