Project Case Study
PaintPlay
A free browser-based coloring app: upload an image, auto-generate line art, and paint with brush, eraser, and bucket fill. Built as a static Next.js export with hand-written Canvas 2D tooling, no login, no database, and no server.
View Live Project →Overview
PaintPlay is a free, browser-based coloring app. The hero states the whole workflow in one line: "Upload an image, auto-generate line art, and paint with brush, eraser, and bucket fill. Export your result as a PNG."
The architectural position is as important as the feature set: no login, no database, no server actions, no API routes. The entire app is a static Next.js export, and every image the user brings stays on their own device. Nothing is uploaded, because there is nowhere to upload it to.
The Design Constraint
A coloring tool for casual users and children has a short patience budget. Every step between "I have a picture" and "I am painting" is a place to lose someone. That produced three rules:
No account. The app opens straight into the tool.
No upload. Privacy is structural rather than promised: the architecture has no server to send an image to.
No leaking. Bucket fill must respect line art the user never drew, which is the hard part.
What This Means for the Business
Photos never leave the device: There is no server or database at all, so every image stays on the user's own device and there is nothing behind the scenes to maintain.
Instant, with no account or install: The app opens straight into the tool, and turning a photo into line art happens right away on whatever device the user already has.
Results that look hand-drawn: Fill stops cleanly at the lines, paint never smears the outline, six textured brushes make the result look drawn rather than filled, and finished pictures save straight to the device as an image.
Feels like a native app on tablets: It installs, runs fullscreen and shows a friendly page when offline, on the device most of its users are actually holding.
Built to be found in search: Themed coloring galleries, guides and landing pages matched to what people search for are all ready-made pages that load quickly.
What This Case Study Demonstrates
Building real graphics tooling on the raw Canvas API instead of reaching for a library
Making privacy an architectural property rather than a policy paragraph
Solving the actual hard problem in a coloring app: fill containment against generated line art
Shipping an installable, offline-capable PWA from a static export
Keeping a dependency surface small enough to audit in one sitting
Live: https://paintplay.app/
Role: Solo delivery (line extraction → canvas engine → tooling → PWA → content/SEO)
