Unity Slot Machine — Extended Version

A feature-rich slot machine built in Unity to demonstrate clean structure, RNG fairness, animation, and bonus mechanics.

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Play (WebGL)

• Open Build/WebGL/index.html locally via a static server.
• Or host the /Build/WebGL folder on GitHub Pages (see below).

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Project Structure

Assets/
  Art/
  Audio/
  Prefabs/
    Reels/
    UI/
  Scenes/
    Main.unity
  Scripts/
    Core/
    Gameplay/
      Reels/
      Symbols/
      Features/
  UI/
  Build/
    WebGL/

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Features

Core Gameplay

• 3×3 reel layout with smooth spin animations
• Win condition: match symbols on paylines
• Paylines: 5 standard lines (3 rows + 2 diagonals)
• Clean RNG (crypto-seeded for fairness)
• Configurable payouts via ScriptableObjects
• Balance system with spin cost and payouts

Bonus Features

• Wild symbols → substitute any match
• Scatter symbols → trigger free spins (3+ scatters)
• Weighted rarity → control symbol frequency
• Animator option → blur reel spin animations

Extensibility

• Paylines easily expanded
• Free spins stackable
• Bonus features isolated in separate scripts
• Fully data-driven using ScriptableObjects

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Scene & Prefab Setup (Step-by-step)

Scene Hierarchy (Main.unity)

Canvas
  ├── UIController (scripts for spin button, balance text)
  ├── SpinButton
  └── BalanceText
SlotMachineController
  └── ReelContainer (empty parent)
       ├── ReelView_0
       ├── ReelView_1
       └── ReelView_2
AudioManager

Prefabs

• Symbol prefab → Image + Symbol script
• Reel prefab → Empty with VerticalLayoutGroup, holds symbols
• UI prefabs → Button, Text

Step-by-step Wiring

1. Create Canvas (UI Scale Mode: Scale With Screen Size).
2. Add Spin Button and Balance Text.
3. Create empty SlotMachineController GameObject → attach SlotMachineController.cs.
4. Inside it, create ReelContainer → add 3 child objects: ReelView_0, ReelView_1, ReelView_2.
5. Each ReelView prefab: attach ReelView.cs.
6. Create Symbol prefab: attach SymbolView.cs, link sprite in inspector.
7. Drag reels and symbols into controller references.
8. Link Spin Button → UIController.OnSpinClicked().

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Unity .gitignore

Add a .gitignore in repo root:

[Ll]ibrary/
[Tt]emp/
[Bb]uild/
[Bb]uilds/
obj/
[Mm]emoryCaptures/
[Bb]in/
/Logs/
*.csproj
*.unityproj
*.sln
*.userprefs
.DS_Store

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🛠 Editor Script (Auto-wire Reels)

Place in Assets/Editor/AutoWireReels.cs:

using UnityEngine;
using UnityEditor;

[CustomEditor(typeof(SlotMachineController))]
public class AutoWireReels : Editor
{
    public override void OnInspectorGUI()
    {
        DrawDefaultInspector();

        SlotMachineController controller = (SlotMachineController)target;
        if (GUILayout.Button("Auto-Wire Reels"))
        {
            var reels = controller.GetComponentsInChildren<ReelView>();
            controller.Reels = reels;
            EditorUtility.SetDirty(controller);
            Debug.Log($"Wired {reels.Length} reels.");
        }
    }
}

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UML-style Class Diagram

classDiagram
    class SlotMachineController {
        - ReelView[] Reels
        - RNGService rng
        - Wallet wallet
        + Spin()
        + EvaluateWin()
    }

    class ReelView {
        - SymbolView[] symbols
        + SpinAnimation()
        + StopAt(SymbolDefinition)
    }

    class SymbolView {
        - SymbolDefinition definition
        + Display()
    }

    class SymbolDefinition {
        <<ScriptableObject>>
        - string name
        - Sprite icon
        - int payout
        - SymbolType type (Normal/Wild/Scatter)
        - int weight
    }

    class RNGService {
        + GetRandomSymbol()
        + Seed()
    }

    class Wallet {
        - int balance
        + Add()
        + Deduct()
    }

    class UIController {
        + OnSpinClicked()
        + UpdateBalanceText()
    }

    SlotMachineController --> ReelView
    ReelView --> SymbolView
    SymbolView --> SymbolDefinition
    SlotMachineController --> RNGService
    SlotMachineController --> Wallet
    SlotMachineController --> UIController

Loading

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Thought Process / Approach

• Started with modular structure (scripts split by domain: core, reels, symbols, features)

• Used ScriptableObjects for symbol definitions & payouts

• Centralized RNGService with cryptographic seeding

• Procedural spin animation with AnimationCurve

• Extended to 3×3 layout with paylines, adding:

  • Wilds (flexible symbol match)
  • Scatters (bonus trigger)
  • Weighted rarity for symbol balancing

• Provided Animator-driven option for motion blur

• Ensured WebGL compatibility

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📚 References

• Unity ScriptableObjects
• Unity UI Toolkit
• AnimationCurve
• Coroutines
• WebGL Build Settings
• Object Pooling

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