diff --git a/Source/Rampage.xcodeproj/project.pbxproj b/Source/Rampage.xcodeproj/project.pbxproj
index 1a78709..7b15af6 100644
--- a/Source/Rampage.xcodeproj/project.pbxproj
+++ b/Source/Rampage.xcodeproj/project.pbxproj
@@ -64,6 +64,7 @@
 		01D0F5D922F80E1600682CA1 /* RampageTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 01D0F5D822F80E1600682CA1 /* RampageTests.swift */; };
 		01D0F5F122FF095E00682CA1 /* Door.swift in Sources */ = {isa = PBXBuildFile; fileRef = 01D0F5F022FF095E00682CA1 /* Door.swift */; };
 		01E3963A2342758D00D02236 /* Pushwall.swift in Sources */ = {isa = PBXBuildFile; fileRef = 01E396392342758D00D02236 /* Pushwall.swift */; };
+		01D0F5EF22FDF19A00682CA1 /* Bitmap+Rendering.swift in Sources */ = {isa = PBXBuildFile; fileRef = 01D0F5EE22FDF19900682CA1 /* Bitmap+Rendering.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -174,6 +175,7 @@
 		01D0F5DA22F80E1600682CA1 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		01D0F5F022FF095E00682CA1 /* Door.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Door.swift; sourceTree = "<group>"; };
 		01E396392342758D00D02236 /* Pushwall.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Pushwall.swift; sourceTree = "<group>"; };
+		01D0F5EE22FDF19900682CA1 /* Bitmap+Rendering.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Bitmap+Rendering.swift"; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -256,6 +258,7 @@
 			children = (
 				016E41B2228E9A5B00ACF137 /* AppDelegate.swift */,
 				016E41B4228E9A5B00ACF137 /* ViewController.swift */,
+				01D0F5EE22FDF19900682CA1 /* Bitmap+Rendering.swift */,
 				01D09AF422A482450052745A /* UIImage+Bitmap.swift */,
 				0199F57323E242D4003E3F08 /* SoundManager.swift */,
 				016E41B6228E9A5B00ACF137 /* Main.storyboard */,
@@ -544,6 +547,7 @@
 			files = (
 				01D09AF522A482450052745A /* UIImage+Bitmap.swift in Sources */,
 				0199F57423E242D4003E3F08 /* SoundManager.swift in Sources */,
+				01D0F5EF22FDF19A00682CA1 /* Bitmap+Rendering.swift in Sources */,
 				016E41B5228E9A5B00ACF137 /* ViewController.swift in Sources */,
 				016E41B3228E9A5B00ACF137 /* AppDelegate.swift in Sources */,
 			);
diff --git a/Source/Rampage.xcodeproj/xcshareddata/xcschemes/Rampage.xcscheme b/Source/Rampage.xcodeproj/xcshareddata/xcschemes/Rampage.xcscheme
index ce33339..edd97b6 100644
--- a/Source/Rampage.xcodeproj/xcshareddata/xcschemes/Rampage.xcscheme
+++ b/Source/Rampage.xcodeproj/xcshareddata/xcschemes/Rampage.xcscheme
@@ -50,7 +50,7 @@
       </Testables>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Release"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"
diff --git a/Source/Rampage/Bitmap+Rendering.swift b/Source/Rampage/Bitmap+Rendering.swift
new file mode 100644
index 0000000..9531e6b
--- /dev/null
+++ b/Source/Rampage/Bitmap+Rendering.swift
@@ -0,0 +1,34 @@
+//
+//  ConcurrentRenderer.swift
+//  Rampage
+//
+//  Created by Nick Lockwood on 09/08/2019.
+//  Copyright © 2019 Nick Lockwood. All rights reserved.
+//
+
+import UIKit
+import Engine
+import Renderer
+
+public extension Bitmap {
+    init(width: Int, height: Int, safeArea: Rect, world: World, textures: Textures) {
+        let cpuCores = ProcessInfo.processInfo.activeProcessorCount
+        var buffers = Array(repeating: [Color](), count: cpuCores)
+        let step = 1.0 / Double(cpuCores)
+        DispatchQueue.concurrentPerform(iterations: cpuCores) { i in
+            let offset = Double(i) * step
+            let range = offset ..< offset + step
+            var renderer = Renderer(
+                width: width,
+                height: height,
+                range: range,
+                textures: textures
+            )
+            renderer.safeArea = safeArea
+            renderer.draw(world)
+            buffers[i] = renderer.bitmap.pixels
+        }
+        let pixels = Array(buffers.joined())
+        self.init(height: height, pixels: pixels)
+    }
+}
diff --git a/Source/Rampage/ViewController.swift b/Source/Rampage/ViewController.swift
index 6063751..4903ae1 100644
--- a/Source/Rampage/ViewController.swift
+++ b/Source/Rampage/ViewController.swift
@@ -132,15 +132,21 @@ class ViewController: UIViewController {
         lastFrameTime = displayLink.timestamp
 
         let width = Int(imageView.bounds.width), height = Int(imageView.bounds.height)
-        var renderer = Renderer(width: width, height: height, textures: textures)
         let insets = self.view.safeAreaInsets
-        renderer.safeArea = Rect(
-            min: Vector(x: Double(insets.left), y: Double(insets.top)),
-            max: renderer.bitmap.size - Vector(x: Double(insets.left), y: Double(insets.bottom))
+        let bitmap = Bitmap(
+            width: width,
+            height: height,
+            safeArea: Rect(
+                min: Vector(x: Double(insets.left), y: Double(insets.top)),
+                max: Vector(
+                    x: Double(width) - Double(insets.left),
+                    y: Double(height) - Double(insets.bottom)
+                )
+            ),
+            world: world,
+            textures: textures
         )
-        renderer.draw(world)
-
-        imageView.image = UIImage(bitmap: renderer.bitmap)
+        imageView.image = UIImage(bitmap: bitmap)
     }
 
     @objc func fire(_ gestureRecognizer: UITapGestureRecognizer) {
diff --git a/Source/RampageTests/RampageTests.swift b/Source/RampageTests/RampageTests.swift
index e001075..69e0625 100644
--- a/Source/RampageTests/RampageTests.swift
+++ b/Source/RampageTests/RampageTests.swift
@@ -17,8 +17,7 @@ class RampageTests: XCTestCase {
 
     func testRenderFrame() {
         self.measure {
-            var renderer = Renderer(width: 1000, height: 1000, textures: textures)
-            renderer.draw(world)
+            _ = Bitmap(width: 1000, height: 1000, world: world, textures: textures)
         }
     }
 }
diff --git a/Source/Renderer/Renderer.swift b/Source/Renderer/Renderer.swift
index 12d1fb0..4d06cd2 100644
--- a/Source/Renderer/Renderer.swift
+++ b/Source/Renderer/Renderer.swift
@@ -12,11 +12,16 @@ private let fizzle = (0 ..< 10000).shuffled()
 
 public struct Renderer {
     public private(set) var bitmap: Bitmap
+    private let width: Int
+    private let range: Range<Double>
     private let textures: Textures
     public var safeArea: Rect
 
-    public init(width: Int, height: Int, textures: Textures) {
-        self.bitmap = Bitmap(width: width, height: height, color: .black)
+    public init(width: Int, height: Int, range: Range<Double>, textures: Textures) {
+        self.width = width
+        self.range = range
+        let columns = Int(Double(width) * (range.upperBound - range.lowerBound))
+        self.bitmap = Bitmap(width: columns, height: height, color: .clear)
         self.textures = textures
         self.safeArea = Rect(min: Vector(x: 0, y: 0), max: bitmap.size)
     }
@@ -25,16 +30,15 @@ public struct Renderer {
 public extension Renderer {
     mutating func draw(_ world: World) {
         let focalLength = 1.0
-        let viewWidth = Double(bitmap.width) / Double(bitmap.height)
+        let viewWidth = Double(width) / Double(bitmap.height)
         let viewPlane = world.player.direction.orthogonal * viewWidth
         let viewCenter = world.player.position + world.player.direction * focalLength
-        let viewStart = viewCenter - viewPlane / 2
+        let viewStart = viewCenter - viewPlane * (0.5 - range.lowerBound)
 
         // Cast rays
-        let columns = bitmap.width
-        let step = viewPlane / Double(columns)
+        let step = viewPlane / Double(width)
         var columnPosition = viewStart
-        for x in 0 ..< columns {
+        for x in 0 ..< bitmap.width {
             let rayDirection = columnPosition - world.player.position
             let viewPlaneDistance = rayDirection.length
             let ray = Ray(
@@ -132,7 +136,7 @@ public extension Renderer {
         let weaponWidth = screenHeight * aspectRatio
         bitmap.drawImage(
             weaponTexture,
-            at: Vector(x: Double(bitmap.width) / 2 - weaponWidth / 2, y: 0),
+            at: Vector(x: Double(width) * (0.5 - range.lowerBound) - weaponWidth / 2, y: 0),
             size: Vector(x: weaponWidth, y: screenHeight)
         )
 
@@ -140,56 +144,65 @@ public extension Renderer {
         let crosshair = textures[.crosshair]
         let hudScale = bitmap.size.y / 64
         let crosshairSize = crosshair.size * hudScale
-        bitmap.drawImage(crosshair, at: (bitmap.size - crosshairSize) / 2, size: crosshairSize)
-
-        // Health icon
-        let healthIcon = textures[.healthIcon]
-        var offset = safeArea.min + Vector(x: 1, y: 1) * hudScale
-        bitmap.drawImage(healthIcon, at: offset, size: healthIcon.size * hudScale)
-        offset.x += healthIcon.size.x * hudScale
+        bitmap.drawImage(
+            crosshair,
+            at: Vector(x: Double(width) * (0.5 - range.lowerBound) - crosshairSize.x / 2,
+                       y: (bitmap.size.y - crosshairSize.y) / 2),
+            size: crosshairSize)
 
-        // Health
         let font = textures[.font]
         let charSize = Vector(x: font.size.x / 10, y: font.size.y)
-        let health = Int(max(0, world.player.health))
-        let healthTint: Color
-        switch health {
-        case ...10:
-            healthTint = .red
-        case 10 ... 30:
-            healthTint = .yellow
-        default:
-            healthTint = .green
-        }
-        for char in String(health) {
-            let index = Int(char.asciiValue!) - 48
-            let step = Int(charSize.x)
-            let xRange = index * step ..< (index + 1) * step
-            bitmap.drawImage(
-                font,
-                xRange: xRange,
-                at: offset,
-                size: charSize * hudScale,
-                tint: healthTint
-            )
-            offset.x += charSize.x * hudScale
-        }
+        var offset = safeArea.min + Vector(x: 1, y: 1) * hudScale
 
-        // Ammunition
-        offset.x = safeArea.max.x
-        let ammo = Int(max(0, min(99, world.player.ammo)))
-        for char in String(ammo).reversed() {
-            let index = Int(char.asciiValue!) - 48
-            let step = Int(charSize.x)
-            let xRange = index * step ..< (index + 1) * step
-            offset.x -= charSize.x * hudScale
-            bitmap.drawImage(font, xRange: xRange, at: offset, size: charSize * hudScale)
+        if range.lowerBound == 0 {
+            // Health icon
+            let healthIcon = textures[.healthIcon]
+            bitmap.drawImage(healthIcon, at: offset, size: healthIcon.size * hudScale)
+            offset.x += healthIcon.size.x * hudScale
+
+            // Health
+            let health = Int(max(0, world.player.health))
+            let healthTint: Color
+            switch health {
+            case ...10:
+                healthTint = .red
+            case 10 ... 30:
+                healthTint = .yellow
+            default:
+                healthTint = .green
+            }
+            for char in String(health) {
+                let index = Int(char.asciiValue!) - 48
+                let step = Int(charSize.x)
+                let xRange = index * step ..< (index + 1) * step
+                bitmap.drawImage(
+                    font,
+                    xRange: xRange,
+                    at: offset,
+                    size: charSize * hudScale,
+                    tint: healthTint
+                )
+                offset.x += charSize.x * hudScale
+            }
         }
 
-        // Weapon icon
-        let weaponIcon = textures[world.player.weapon.attributes.hudIcon]
-        offset.x -= weaponIcon.size.x * hudScale
-        bitmap.drawImage(weaponIcon, at: offset, size: weaponIcon.size * hudScale)
+        if range.upperBound == 1 {
+            // Ammunition
+            offset.x = safeArea.max.x - range.lowerBound * Double(width)
+            let ammo = Int(max(0, min(99, world.player.ammo)))
+            for char in String(ammo).reversed() {
+                let index = Int(char.asciiValue!) - 48
+                let step = Int(charSize.x)
+                let xRange = index * step ..< (index + 1) * step
+                offset.x -= charSize.x * hudScale
+                bitmap.drawImage(font, xRange: xRange, at: offset, size: charSize * hudScale)
+            }
+
+            // Weapon icon
+            let weaponIcon = textures[world.player.weapon.attributes.hudIcon]
+            offset.x -= weaponIcon.size.x * hudScale
+            bitmap.drawImage(weaponIcon, at: offset, size: weaponIcon.size * hudScale)
+        }
 
         // Effects
         for effect in world.effects {