Daniel Sonnenberg

Freelancer · Remote

DanielSonnenberg

Fullstack developer with a strong design focus.

Get in touch
Fig. 01 Exploded view

Five layers.

Infrastructure · Data · Logic · Interfaces · Design & Interface: I build all of them. Touch a layer for details.

Fig. 01 Assembled

One product.

Concept, design, code, operations: from one pair of hands, with one responsibility.

02Sheet 02 / 07 · Evidence

Evidence, not claims.

Public projects are linked and can be checked directly. Projects under NDA are anonymised, but described honestly.

#1on Google for the German search term „digitale Stempelkarte" with my own SaaS Hillcard, built solo and grown organically.
Top 3contributor to IHP by lines added. Open source, publicly visible.
since 2018publisher on the Unity Asset Store, today with AI Forge and Easy UI among others.
since 2015websites and software for clients: employed, self-employed and as a co-founder.

Public · linked · verifiable

2020–2022Open source

IHP, Integrated Haskell Platform

Web framework in Haskell, open source. As a developer at digitally induced I helped build the core. The contributions are public and predate AI autocomplete: top 3 by lines added.

HaskellFramework coreOpen source
Role: core contributorRepository →
since 2023Own SaaS

Hillcard, digital loyalty card

My own product, entirely solo: concept, design, fullstack in IHP, launch, operations. Today ranked #1 on Google for the German search term „digitale Stempelkarte", organically.

IHP / HaskellSaaSLaunch & operationsSEO
Role: everythinghillcard.de →
since 2018Asset Store

AI Forge & Easy UI, Unity assets

My own tools on the Unity Asset Store: AI Forge (Free & Pro) connects AI agents directly to the Unity project, no MCP server needed. Easy UI builds Unity UI via AI with far more code control than the standard UI. Plus an older asset from 2018 that combines vehicle and character controllers.

Unity / C#AI toolingProduct
Role: development & salesPublisher page →

Confidential · anonymised · details in conversation

Under NDA

Compliance platform for a data-protection consultancy

IndustryData protection / compliancePeriod2020–2022 (at digitally induced)RoleConcept through maintenance, client contactStackHaskell / IHP

Starting point

A data-protection consultancy needed its own tool for its clients: checklists, evidence and management functions that previously ran through documents and e-mails, error-prone and hard to scale.

My part

I was responsible for the product from concept through design and development to deployment and maintenance, including direct client contact and ongoing updates over several years.

Result

A production platform that carries the consultancy through its day-to-day business. What exactly it does and for whom stays under wraps for good reason. In conversation I am happy to share what transfers.

Case studyNo screenshots, no names. Discretion is part of the service.
Confidential

Inspection and documentation app for fall-protection systems

IndustryOccupational safety / building technologyPeriod2020–2022 (at digitally induced)RoleDevelopment, web & mobileStackReact, React Native, iOS & Android

Starting point

Fall-protection systems have to be inspected regularly and documented without gaps: on the roof, often without network, with liability consequences for mistakes.

My part

Contributed to the software for inspection and documentation: a web application plus native apps for iOS and Android, so inspectors can work on site and the documentation arrives cleanly in the office.

Result

A tool that mirrors inspection practice instead of obstructing it. The client stays unnamed here, but the mechanics of offline capability, inspection reports and chain of evidence transfer to many industries.

Case studyCross-platform: one codebase, three platforms.

Further work · selection

07Driving-school practice simulatorMobile app for the driving-school market, developed entirely solo: driving physics, scenarios, evaluation.Unity · iOS & Androidsince 2023
08Search engine for a property portalBuilt the search in the early phase of a portal for commission-free property.Haskell / IHP2020–2022
09Photo booth, hardware & softwareDeveloped and built for a client: controls in Python on a Raspberry Pi, enclosure via CAD. Software that needs a housing.Python · Raspberry Pi · CADsince 2023
10Client websites via hillcodeWebsites for trades, retail and services, handled through the company.hillcode.de →since 2023

“Daniel was responsible for our platform from the first sketch to day-to-day operations. We never had to explain what we meant twice.”

Management, data-protection consultancy

“The app has run reliably for years, on the roof just as much as in the office, offline included. We barely notice it these days, except when a new feature arrives.”

Project lead, building technology
03Sheet 03 / 07 · Approach

Engineering rules.

Six rules I build by, regardless of stack, industry or team size. They are the reason my projects keep working after the handover.

01

Design and engineering are one trade.

I don’t split into “design first, then implementation”. An interface that doesn’t hold up technically isn’t good design, and engineering that feels wrong isn’t finished. I do both, which is why they fit together.

02

One responsibility instead of many handovers.

Concept, data model, backend, frontend, deployment, maintenance: when one person knows the whole chain, the friction between trades disappears. And there is someone who is actually in charge.

03

The stack follows the problem.

I have used Haskell, Next.js, Django, Unity and more in production. I choose what fits the team, the runtime and the budget, not what is in fashion or what I used last.

04

Readable in two years.

The code I write will be read by someone who didn’t write it, often by me, later. Clear structure, boring solutions in the right places, tests where they actually protect something.

05

Built, not generated.

I use AI like a sharp tool: fast, gladly, daily, and I still answer for every line. My foundations come from the time before. That is why I can tell when a suggestion looks good and is still wrong.

06

Discretion is part of the service.

A large part of my work is under NDA. I treat your project the same way: no logos without approval, no screenshots, no anecdotes at conferences. What you show me stays with me.

Process · how a project with me runs
01

Conversation

What should be built, for whom, with what budget and horizon? I say early whether I’m the right person, or who would be.

1 meeting
02

Concept

Structure, data model, interface and technology in one document you can actually understand. With clear assumptions and an honest estimate.

Days
03

Design & build

Iteratively, in short rounds. You see real builds regularly instead of slides and can change course while it is still cheap.

Weeks
04

Launch

Deployment, domain, monitoring, handover. Documented so that someone else could carry on.

Days
05

Operations

Maintenance, updates, further development: permanently if you like, otherwise with a clean handover to your team.

As needed
04Sheet 04 / 07 · About

Two roles, one responsibility.

I’m a fullstack developer because the whole chain interests me: from the data model to the last pixel. And I’m a designer because I can’t ship software that feels wrong.

It started at the age of eight, with my first own programs. At 14 I built websites for a company on the side. After the Abitur in 2018 I went into computer science, and from the second semester into practice as a working student, soon full-time. At digitally induced I developed in Haskell for two years, helped build the open-source framework IHP and was responsible for client products from concept to maintenance.

In 2023 I co-founded hillcode with a partner. That is where our own products come from, such as Hillcard and the Unity assets, as well as client projects. As a freelancer I work for startups, SMEs, agencies and corporations: wherever someone is needed who thinks design and engineering as one.

  • since childhoodFirst own programsStarted at eight, never stopped.
  • 2015 – 2019First websites for a companyOn the side, during school. HTML, CSS, WordPress.
  • 2018Abitur · start of Applied Computer ScienceTU Dortmund University.
  • 02/2020 – 10/2022digitally induced GmbH, fullstack developerHaskell/IHP, core contributor to the open-source framework, client products end to end, web and mobile apps.
  • 2022 → todayMedia Informatics, TH Köln (part-time)Moved from Dortmund to Cologne. Runs alongside continuous full-time practice.
  • since 03/2023hillcode, co-founderOwn products (Hillcard, Unity assets), client projects, hardware. Sonnenberg & Schimpf Softwareentwicklung GbR.
  • todayFreelance, fullstack with a design focus
05Sheet 05 / 07 · Tools

What I can do, sorted by depth.

What I use daily, and what I have used in production. If your stack isn’t listed: I get up to speed quickly, the stack is rarely the hard part.

Core · daily, in depth
  • 01Haskell · IHPType-safe and fast. My home since 2020: framework core, Hillcard, client platforms.
  • 02Next.js · React · TypeScriptFor everything that needs a large ecosystem and many hands.
  • 03Django · PythonBackends, internal tools, automation and everything that talks to hardware.
  • 04Unity · C#Apps, simulations, tooling. Own assets on the store since 2018.
  • 05Design · UI/UXFrom concept to design system. Not a separate trade but part of every build.
  • 06Hardware · electronics · CADFrom PCB design and SMD soldering via ESP32 and Raspberry Pi to CAD (Fusion 360). Software that needs a housing.
Other languages · fluent
C / C++SwiftKotlinJavaGLSL
Experience with · used in practice
React NativeStatic HTML/CSSSQL · PostgreSQLDeployment · CI · hosting
Briefly used · seen
Laravel / PHPAngularVueSvelteWordPressand more

Depth ratings are self-assessment. Ask me for details in conversation. I will also tell you what I can’t do.

06Sheet 06 / 07 · Media

Design doesn’t end at the interface.

Software often comes with the moving image that explains it. Product and marketing videos, motion design and 3D: from concept through shooting to the final cut, from one pair of hands.

01

Product & marketing

Videos and key visuals that make a product understandable: for startups, landing pages and campaigns. Most recently marketing videos for Hillcard and the IHP casts, from planning through shooting to the edit.

02

Motion & 3D

Animation and 3D scenes in Blender and Cinema 4D. From logo bumper via explainer animation to product visualisation, when a real photo isn’t enough.

03

Post-production

Editing, colour grading and sound in DaVinci Resolve, Premiere Pro and After Effects. The part that turns raw footage into a finished video.

Tools · design, editing, 3D
PhotoshopIllustratorAfter EffectsPremiere ProDaVinci ResolveFinal Cut ProCinema 4DBlender
07Sheet 07 / 07 · Contact

Let’s talk about your project.

An e-mail is enough. Write what should be built and within what frame. I answer honestly, even if the answer is that someone else fits better.

E-mail · direct, no form
daniel@hillcode.deWhat for · typical occasions
  • 01A product from zero to one: concept, design, fullstack, launch. One person, one responsibility.
  • 02Design and implementation from one pair of hands, when the handover between agency and development used to be the expensive part.
  • 03Building on what exists: interim in the team, a feature nobody wants to touch, or a migration.
  • 04Consulting: architecture, stack choice, feasibility. Also as a second opinion.

End-customer websites (trades, retail, practices) run via hillcode.de. That is the right place if you need a company website.

Evidence · to verify
GitHubPublic code, including contributions to IHP.github.com/nezbiteUnity Asset StoreAI Forge, Easy UI and more. Publisher page.Publisher 41949HillcardMy own SaaS, live.hillcard.dehillcodeThe company, with client references.hillcode.de
§Legal

Legal notice & privacy.

Legal notice (Impressum)

Information pursuant to § 5 DDG (German Digital Services Act)

Sonnenberg & Schimpf Softwareentwicklung GbR
Petersweg 12
88214 Ravensburg

Authorised representatives (partners): Daniel Sonnenberg, David Schimpf

E-mail: daniel@hillcode.de
Web: hillcode.de

VAT identification number pursuant to § 27a UStG: DE367222829

Responsible for content: Daniel Sonnenberg, address as above.

Privacy

This site sets no cookies and uses no tracking or analytics services. There is no contact form; if you e-mail me, I process your details solely to answer your enquiry.

The site runs on my own server at netcup GmbH, Karlsruhe, Germany. When you visit, technically necessary access data (IP address, time, requested file, browser identifier) is processed in server logs and deleted after 14 days at the latest. The legal basis is Art. 6 (1) (f) GDPR, the legitimate interest in secure operation.

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Controller within the meaning of the GDPR: see legal notice. You have the right to access, rectification, erasure and restriction of processing of your data, as well as the right to lodge a complaint with a supervisory authority.