Cengizhan Koçal Available · UTC+3

React · TypeScript · React Native · Node

Software people play with, built to be measured.

I’m Cengizhan, a developer with six years in React and TypeScript. These are four products I built end to end — a dashboard, a mobile app, a content site and an API. Each one is live, open source, and checked by its own tests before it ships.

Live products
4
Automated checks
322
Lighthouse, mobile
87–100

Selected work

Four products, four kinds of job

Dashboard · Vite + React

Balance — a grid control room

For your SaaS admin panel, ops console or analytics dashboard: live KPIs, charts you can press, a table that filters and exports, roles and an audit log.

  • A 3D model of the region where power visibly moves; press a plant to take it out and every page re-solves.
  • A Sankey from fuel to demand, a price surface across a lever’s range, fleet gauges — all from one model, nothing typed in.
  • Sign-in with roles, an audit log and CSV export on a small Cloudflare API.
  • React 19
  • TypeScript
  • React Three Fiber
  • TanStack Table
  • shadcn/ui
  • Cloudflare D1

Lighthouse mobile 87–90 · 62 unit and 68 browser tests · axe 0 violations

Mobile app · Expo + React Native

Tilt — an offline neon arcade

For your mobile MVP: one codebase for iPhone, Android and the web, with the sensors, haptics, sound and 60 fps motion that make an app feel native.

  • Seven games; Roll is played by tilting the phone — the gravity sensor read on the UI thread, levelled to your grip.
  • The cabinet’s cards lean with the phone; a daily challenge with a streak; scores kept offline.
  • Runs on a real iPhone from a Release build; the web build is the same code.
  • Expo SDK 58
  • React Native
  • Skia
  • Reanimated
  • Zustand

Lighthouse mobile 96–97 on the web build · 41 unit and 26 browser tests

Content site · Next.js

Datum — a journal with live drawings

For your blog, magazine, documentation or company site: posts your team writes as files, search, topics, a feed and share cards — with interactive pieces inside the article.

  • A 3D cover where you drag the sun across the day; on a phone it plays as a video rendered from the scene.
  • A sunlight-hours study of the ground, ray-cast at build time; a section you cut; the building in AR on your desk.
  • MDX posts, ⌘K search, topics, RSS, sitemap and a generated share card per post.
  • Next.js 16
  • React Three Fiber
  • MDX
  • Tailwind CSS 4

Lighthouse mobile 88–94 · 60 unit tests and five browser QA passes · axe 0 violations

Backend API · Cloudflare Workers

Slot — bookings that cannot double-book

For your booking, scheduling or appointments product: availability across time zones, holds and payments, webhooks your other systems can trust, and docs developers can start from.

  • Capacity checked inside one SQL statement; five simultaneous requests, exactly one wins — tested at the database.
  • Time zones through Intl alone, idempotent retries, HMAC-signed webhooks retried on a schedule you can watch.
  • A developer portal: quickstart, OpenAPI 3.1 reference, error catalogue, live status and a playground.
  • Hono
  • Cloudflare Workers
  • D1 (SQLite)
  • Zod
  • OpenAPI 3.1

Lighthouse 100 on every portal page · 65 tests inside workerd

How I work

What you get besides the screens

  1. The first thing you see is the product. Motion, depth and something to press on the first screen — then the details that hold up when someone looks closer.
  2. Measured on a phone. Lighthouse and accessibility checks on every page, on the live URL, before I call it done.
  3. Tests that would catch the bug. Each fix comes with a test shown failing without it.
  4. Small, readable steps. Short updates, a live link at each milestone, and a handover README a new developer can run from.

Have something like this in mind?

Tell me what it has to do and who it is for — a dashboard, an app, a site or the API behind them. I work from Turkey, UTC+3, and overlap with European and US East Coast mornings.

Find me on GitHub