Mobile Game Development Basics

# CHAPTER 14

Mobile Game Development Basics #

1. Introduction #

2. Learning Objectives #

• Switch a Unity project's build target from PC to Android/iOS.

• Read multi-touch screen inputs using Input.touches.

• Implement virtual on-screen UI joysticks and buttons.

• Optimize graphics settings for low-end mobile hardware.

• Build an Android APK file for device testing.

3. Switching the Build Platform #

1. 1. Go to File -> Build Settings.

1. 2. Under "Platform", select Android (or iOS).

1. 3. Click the Switch Platform button. Unity will take a few minutes to re-compress all your audio and textures into mobile-friendly formats.

4. Reading Touch Input (The Raw Way) #

void Update()
{
    // Are there any fingers on the screen?
    if (Input.touchCount > 0)
    {
        // Get the data for the first finger that touched the screen (Index 0)
        Touch touch = Input.GetTouch(0);

        // Did the finger just tap the screen this exact frame?
        if (touch.phase == TouchPhase.Began)
        {
            Debug.Log("Screen Tapped at coordinate: " + touch.position);
            Jump();
        }
    }
}

5. On-Screen UI Joysticks #

1. 1. Open the Package Manager (Window -> Package Manager).

1. 2. Install the Device Simulator or the Standard Assets (CrossPlatformInput) (depending on your Unity version).

1. 3. Alternatively, search the Asset Store for "Free Mobile Joystick".

1. 4. You simply drag the UI Joystick Prefab onto your Canvas.

1. 5. In your C# code, instead of Input.GetAxis("Horizontal"), you change it to FixedJoystick.Horizontal. The transition takes 5 seconds and perfectly maps your PC movement code to a touch screen!

6. Mobile Optimization (Crucial Step) #

• Shadows: Real-time shadows are incredibly expensive on mobile. Go to Edit -> Project Settings -> Quality, and change Shadows to Hard Shadows Only, or disable them completely and use "Baked" (pre-painted) lighting.

• Poly Count: A PC character can have 50,000 polygons. A mobile character should be kept under 10,000.

• Post-Processing: Avoid heavy effects like Depth of Field or Ambient Occlusion on mobile.

7. Building an Android APK #

1. 1. Ensure your phone is plugged in via USB and "Developer Options / USB Debugging" is enabled on the device.

1. 2. In Unity, go to Edit -> Project Settings -> Player.

1. 3. Under the Android tab, set the Company Name and Product Name.

1. 4. Set the Minimum API Level (e.g., Android 8.0).

1. 5. Go to File -> Build Settings.

1. 6. Click Build and Run. Unity will compile the C# code into a .apk file, push it through the USB cable, and instantly launch the game on your phone!

8. Visual Learning: Touch Phases #

A single finger touch transitions through "Phases":

1. TouchPhase.Began      -> (Frame 1: Finger touches the glass)
2. TouchPhase.Moved      -> (Finger drags across the screen)
3. TouchPhase.Stationary -> (Finger rests, not moving)
4. TouchPhase.Ended      -> (Finger is lifted off the glass)

9. Best Practices #

• Device Simulator: You don't have to build an APK every time you want to test mobile UI. Unity has a built-in Device Simulator window (accessible next to the Game tab). It overlays a virtual iPhone or Samsung bezel over your game, allowing you to perfectly test UI Safe Areas (preventing UI from being hidden under the camera notch) right in the editor.

10. Common Mistakes #

• Assuming Mouse = Touch: In the Unity Editor, clicking the mouse emulates a touch, making it easy to test. However, relying on Input.GetMouseButtonDown(0) in your final mobile build can cause weird glitches on multi-touch devices. Always switch to true Input.touches logic before publishing a mobile game.

11. Mini Project: Convert to Mobile Controls #

1. 1. Create a Canvas with two Buttons anchored to the bottom corners. Label them "Left" and "Right".

1. 2. Add an EventTrigger component to each button. This allows us to detect when the button is *held down*, not just clicked once.

1. 3. Create a MobileController script:

public class MobileController : MonoBehaviour
{
    public float speed = 5f;
    private int moveDirection = 0; // -1 for left, 1 for right, 0 for stop

    void Update()
    {
        transform.Translate(moveDirection * speed * Time.deltaTime, 0, 0);
    }

    // Connect these to the UI EventTriggers (PointerDown / PointerUp)
    public void PressLeft() { moveDirection = -1; }
    public void PressRight() { moveDirection = 1; }
    public void ReleaseButton() { moveDirection = 0; }
}

1. 4. Map the UI Event Triggers to these functions. You can now steer your character using your thumbs on the screen!

12. Practice Exercises #

1. 1. What menu option must you select to reconfigure Unity's backend from compiling .exe files to compiling .apk files?

1. 2. If you want to run code only on the exact frame a player's finger lifts off the glass, which TouchPhase should you check for?

13. MCQs with Answers #

14. Interview Questions #

• Q: Explain the lifecycle of a mobile touch input via the TouchPhase enum. How do Began, Moved, and Ended correlate to standard mouse clicks?

• Q: A PC game port is running at 15 FPS on a modern smartphone. Detail three specific rendering optimizations you would perform in the Unity Editor to drastically improve performance.

• Q: Describe the workflow for testing mobile UI responsiveness in the Unity Editor without having to build to a physical device every 5 minutes.

15. FAQs #

16. Summary #

17. Next Chapter Recommendation #