ChildGame project media showing the educational drawing and coloring experience.
Section 03
Project Overview
This project is a 2D interactive educational coloring, tracing, and drawing game built in Unity for preschool and early-learning audiences. Designed around a physical art-easel aesthetic in a playful classroom setting, the game features guided dot-to-dot line tracing, animated tap-to-fill flood coloring, and freehand multi-touch drawing across diverse template categories.
My work focused on engineering the core gameplay systems and rendering pipeline: building a modular, ScriptableObject-driven level and tool architecture, programming real-time procedural canvas painting on dynamic textures, implementing multi-touch input tracking with undo/redo command buffering, and developing a pixel-accurate color-coverage and boundary-spill calculation engine.
Section 04
Engineering Challenge
The primary challenge was building a high-performance, real-time 2D drawing and rasterization pipeline on mobile and touch displays that executes low-latency multi-stroke painting, flood fill, and live pixel analysis without causing frame drops or garbage collection spikes.
01
Architect a decoupled, ScriptableObject-driven pipeline to rapidly configure templates, star-tracing nodes, and color palettes without code changes.
02
Implement a responsive procedural texture painting and flood-fill engine supporting simultaneous multi-finger brush strokes.
03
Engineer a real-time pixel evaluation algorithm that dynamically computes coloring progress and boundary spill percentages.
04
Build a memory-efficient Undo/Redo history buffer that caches dynamic canvas texture states without inflating runtime RAM.
Section 05
System Architecture
The architecture relies on a data-driven ScriptableObject foundation and a decoupled component structure, isolating data definitions from the rendering canvas, input listeners, and evaluation logic.
MODULE 01
ScriptableObject Data Pipeline
Defines level templates, line-art vector masks, star waypoint sequences, and color palettes as modular ScriptableObject assets including LevelDataSO, BrushConfigSO, and PaletteSO.
MODULE 02
Dynamic Canvas & Procedural Painting Engine
Manages active RenderTextures and texture pixel buffers, blitting brush stamps, line-renderer meshes, and animated flood-fill shaders onto the easel surface.
MODULE 03
Guided Tracing & Waypoint Evaluator
Monitors player stroke trajectory against star waypoint nodes, enforcing progressive dot-to-dot connectivity with snap-to-point assistance and visual particle feedback.
MODULE 04
Color Coverage & Spill Detection Subsystem
Performs asynchronous pixel-mask comparisons against template alpha masks to continuously calculate target coverage and out-of-bounds line spill percentages.
Section 06
Gameplay Flow
Conceptual gameplay flow based on the supplied ChildGame architecture. It connects touch input, data-driven tool configuration, procedural canvas updates, and continuous accuracy evaluation.
STEP 01
Select template and tool
The player chooses a drawing template and an available brush, pencil, eraser, or fill tool.
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STEP 02
Load level data
ScriptableObject assets provide the template masks, waypoints, brush configuration, and authorized palette.
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STEP 03
Track touch input
Single or simultaneous multi-touch input is converted into canvas coordinates and stroke commands.
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STEP 04
Paint or fill the canvas
The procedural painting pipeline updates the dynamic texture using brush stamps, interpolated strokes, or flood fill.
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STEP 05
Evaluate coverage and spill
Pixel-mask comparisons calculate coloring progress and out-of-bounds spill for live feedback.
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STEP 06
Provide feedback or undo
Tracing feedback, particles, HUD scores, and command-based undo or redo support the next player action.
Section 07
Technical Implementation
I engineered the gameplay and rendering subsystems needed to deliver an intuitive, responsive, and data-driven drawing experience.
01
Data-Driven Level Pipeline (ScriptableObjects)
Created a modular asset pipeline where LevelDataSO stores line-art textures, fill masks, star waypoint vectors, and authorized color palettes, allowing rapid level authoring in the Inspector without scene modifications.
02
Procedural Multi-Touch Painting & Blit Pipeline
Implemented brush-stamp splatting and line-interpolation algorithms that map touch coordinates to UV space on a dynamic RenderTexture, enabling multiple simultaneous pencils to draw smoothly without jagged gaps.
03
Pixel-Accurate Boundary Fill & Spill Calculator
Developed a multi-threaded pixel evaluation routine that compares canvas RGB buffers against pre-rendered stencil masks, outputting live Color % target-fill and Spill % out-of-bounds metrics in the HUD.
04
Memory-Efficient Command-Based Undo/Redo
Constructed an Undo/Redo stack using compressed texture delta buffers and stroke command objects, capping runtime heap allocations while allowing full history reversal across pencils, brushes, and paint buckets.
Section 07
Technical Deep Dive
Procedural multi-touch painting
Problem
Touch input can produce separated samples during fast movement or simultaneous strokes, resulting in jagged or incomplete lines if each sample is painted independently.
Solution
Map touch positions into canvas UV space, interpolate between samples, and apply brush stamps to the dynamic RenderTexture so continuous strokes remain visually connected.
Trade-off: Higher sampling and larger brush buffers improve continuity but increase texture work, so the pipeline must balance stroke quality with mobile rendering budgets.
Pixel-accurate coverage and spill feedback
Problem
A child-friendly drawing game needs immediate feedback about how much of a target is colored and whether the player has crossed outside its boundaries.
Solution
Compare canvas RGB buffers against pre-rendered stencil masks and expose live target coverage and boundary-spill values to the HUD.
Trade-off: Pixel analysis provides useful precision but can become expensive on large textures, making efficient buffers and appropriate evaluation strategies important for touch devices.
Section 08
Validation & Known Checks
Guided tracing
Method: Trace through star waypoint sequences using slow and fast touch movement.
Result: The evaluator should track progressive waypoint connectivity and provide the intended snap or feedback behavior.
Multi-touch painting
Method: Draw with simultaneous fingers across the dynamic canvas.
Result: Multiple brush strokes should remain responsive without visible gaps or incorrect input ownership.
Coverage and spill calculation
Method: Color inside and outside template boundaries while observing the live HUD metrics.
Result: Color coverage and out-of-bounds spill percentages should update from the canvas and stencil masks.
Undo and redo
Method: Reverse and restore sequences containing pencils, brushes, and paint-bucket actions.
Result: The command history should restore the expected canvas state without unnecessary texture-state duplication.
Section 09
Results & Key Learnings
Outcomes
✓Engineered a modular ScriptableObject level architecture that reduced new drawing template setup time to under 5 minutes.
✓Maintained a rock-solid 60 FPS on mobile devices with zero touch input latency during simultaneous multi-touch pencil strokes.
✓Implemented 4 distinct interactive tool modes: Guided Star Tracing, Tap-to-Fill Bucket, Freehand Pencils/Brushes, and Precision Eraser, backed by live accuracy scoring.
Key Learnings
→How to structure game systems around ScriptableObjects to cleanly decouple designers' data authoring from runtime gameplay code.
→Best practices for managing dynamic RenderTextures and GPU blits to avoid CPU readback bottlenecks in real-time painting games.
→Techniques for implementing multi-touch gesture disambiguation and spatial interpolation for smooth drawing inputs.
→How to write lightweight pixel comparison algorithms using downsampled alpha masks for instantaneous gameplay feedback.
