Systems Builder · Lithuania

I turn messy workflows into structured digital systems.

I build practical tools, dashboards and automation workflows for complex work — from Excel-based estimation systems and technical dashboards to AI-assisted apps and internal business tools.

View projects → Work with me
// What I build

Four areas. One mission.

I connect AI, Excel, automation and product thinking into practical systems that save time and create real leverage.

01
🤖

AI-assisted tools

Practical web apps and workflows that use AI where it creates real leverage — not as decoration, but as genuine productivity gain.

02
📊

Excel & estimation systems

Advanced spreadsheets, BOQ logic, dashboards, work norms and technical classification systems for complex projects.

03
⚙️

Automation workflows

OpenAI API, Claude API, Google Sheets, custom integrations and AI-assisted process automation that eliminates repetitive work.

04
🎨

Technical-creative systems

Interactive concepts, visual tools, product prototypes and creator-focused workflows that bridge logic and design.

// Featured projects

Systems, not screenshots.

Each project solves a real workflow problem — not a design exercise.

Electrical Estimation Systems

Professional workflow

Structured Excel and estimation workflows for electrical and industrial projects — BOQ mapping, cable classification, work norms and bid preparation logic built over years of real-world use.

Speeds up technical bid preparation and significantly reduces manual errors on complex tenders.

Excel BOQ logic Classification Estimation Power BI

Volt* Electrical Engineering Suite

3 live tools

A suite of three electrical engineering tools built around IEC standards, BOQ workflows and cable optimization logic — combining deterministic decision engines with practical cost and compliance analysis.

Turns complex electrical material decisions into structured, auditable workflows with traceable recommendations and export-ready outputs.

React TypeScript Python IEC 60364-5-52 BOQ logic Excel export Google Cloud Run
VoltAnalyze screenshot
VoltAnalyze
BOQ analysis & review workflow. AUTO/REVIEW/REJECT decision logic with confidence scoring and audit trail.
Open →
VoltOptic screenshot
VoltOptic
Cable optimization engine. Cu→Al replacement recommendations with IEC 60364-5-52 compliance and export report.
Open →
VoltOptimize screenshot
VoltOptimize
Cable selection & cost optimization matrix. Ampacity checks, voltage drop, material comparison and Value Engineering Guide.
Open →

MedShelf

Live · medshelf.life

A medicine tracking PWA for caregivers — doses, schedules, refills and interaction warnings for every family member, all in one place. Built with offline support and a clean mobile-first UI.

Reduces medication errors and gives caregivers clarity over complex household health routines.

React TypeScript Supabase PWA Tailwind shadcn/ui
MedShelf app screenshot
Open app →

ColdStock

Live · coldstock.site

A fridge and freezer inventory PWA that tracks food items, expiry dates and shopping lists from any device. Built with a dark mobile-first UI and offline support.

Reduces food waste and helps households stay organised without mental overhead.

React TypeScript Supabase PWA Tailwind
ColdStock app screenshot
Open app →

CleanStock

Live · cleanstock.app

A household cleaning inventory PWA — tracks cleaning supplies, expiry dates and shopping lists from any device. Companion app to ColdStock with a shared design system.

Eliminates the "we ran out again" problem by keeping household supplies visible and organised.

React TypeScript Supabase PWA Paddle
CleanStock app screenshot
Open app →

Email Spruce

Live · emailspruce.com

An AI email assistant for busy professionals — generates professional, high-quality email replies from context. Built with Supabase auth and session persistence for seamless daily use.

Saves hours on email drafting by turning short notes into polished, professional responses.

React TypeScript Supabase OpenAI API Lovable
Email Spruce screenshot
Open app →

QuickTools

Live · 100+ utilities

A collection of 100+ client-side web utilities for developers, designers and everyday use — calculators, converters, formatters and productivity tools, all running in the browser without any backend.

Demonstrates rapid tool-building ability — 100+ utilities built and shipped as a single fast web app.

React TypeScript Vite Tailwind Client-side
QuickTools screenshot
Open app →

Hull Renewal Compass

Live tool

A vessel survey and hull inspection management tool built for a marine company — structured checklists, compliance tracking, client contacts, media uploads and custom fields for each survey.

Turns unstructured vessel inspection workflows into a structured, repeatable digital process with full audit trail.

React TypeScript Supabase Lovable Compliance logic
Hull Renewal Compass screenshot
Open app →

Receipt Rocket

Live tool

An AI-powered receipt scanner and expense tracker — camera capture, automatic categorisation, budget management, analytics and export. Built for individuals and small teams tracking real spending.

Eliminates manual expense entry by turning receipt photos into structured, categorised financial data.

React TypeScript AI scanning Lovable Analytics
Receipt Rocket screenshot
Open app →

Excel & Dashboard Toolkit

Real working systems

Custom dashboards, Gantt tools, calculators and workflow systems built with advanced Excel logic. Covers project management, financial tracking, resource planning and reporting.

Transforms spreadsheet-heavy work into structured decision-making systems with clear outputs.

Excel Power BI Google Sheets Dashboards
// How I work

Five steps. Every project.

My edge isn't just the tools — it's the structured thinking behind every system I build.

01

Map

Understand the real workflow, not just the visible task. Find where the friction actually lives.

02

Structure

Classify data, decisions, exceptions and rules. Build the logic before writing any code.

03

Build

Create dashboards, tools, prototypes or automations that match the real use case exactly.

04

Stress-test

Check edge cases, user behaviour and weak assumptions before calling anything done.

05

Improve

Add AI only where it creates real leverage — not as decoration, but as genuine force multiplier.

// Services

Three things I do well.

I'm not an agency. I'm a specialised systems builder who works directly with you.

🔍

Workflow & automation audit

For businesses with manual, repetitive or spreadsheet-heavy processes. I map what you do, identify what can be automated, and deliver a clear action plan.

📈

Excel-to-system transformation

I take spreadsheet-heavy workflows and turn them into clearer dashboards, calculators, internal tools or web apps — with the same logic, better structure.

🚀

AI product prototyping

For founders, teams or creators who want to test an internal tool or SaaS idea quickly. Fast MVPs with real architecture — not throwaway demos.

17+
Years 3D & technical visualisation
10+
Live apps & tools built
3+
Years estimation systems
3+
Industry domains covered
React TypeScript Supabase Python Excel Google Sheets OpenAI API Claude API Lovable Claude Code 3D visualisation
// About

I work where spreadsheets, workflows, product thinking and automation overlap.

I'm Gintaras Jonika — a technical-creative systems builder from Lithuania. My background in 3D visualisation, technical estimation and Excel architecture helps me see both sides of a system: the logic underneath and the experience of the person using it.

I'm most useful when the work is messy, manual, spreadsheet-heavy or hard to structure — and needs to become clear, repeatable and usable.

Based in Lithuania · Working globally
// FAQ

Common questions.

What exactly is a systems builder — and how is it different from a developer? +

A developer writes code. A systems builder first maps the real workflow — where the friction lives, what the data actually is, what decisions need to happen — and then builds the right tool for that. I spend as much time on structure and logic as on the code itself. The result is something that fits how you actually work, not just a generic app.

How do I convert an Excel spreadsheet into a web app? +

The process starts by mapping what the spreadsheet actually does — its logic, decision rules, exceptions and outputs. Then I rebuild that logic in a structured web app (React + Supabase) with proper data storage, user access and a clean interface. The goal is not a pixel-perfect copy of the spreadsheet — it's a better version of the same workflow.

Can you automate BOQ and electrical estimation workflows? +

Yes — this is one of my core areas. I have 3+ years building estimation systems for electrical and industrial projects: BOQ mapping, cable classification, work norms, bid preparation logic and IEC compliance checks. I build both Excel-based systems and web tools like VoltAnalyze, VoltOptic and VoltOptimize that handle these workflows programmatically.

How long does it take to build an internal tool or MVP? +

A focused MVP with one core workflow — auth, data storage, basic UI — typically takes 1 to 3 weeks depending on complexity. A more complete tool with multiple views, role-based access and integrations is usually 4 to 8 weeks. I work in tight iterations and show progress early, so you're never waiting weeks to see something.

Do you work with non-technical clients? +

Yes. Most of my clients describe their problem in plain language — "we track this in Excel and it keeps breaking", "our estimator spends 3 days on every bid". I translate that into a structured system. You don't need to know what React or Supabase is to work with me effectively.

What is a PWA and why build one instead of a native app? +

A PWA (Progressive Web App) runs in the browser but can be installed on a phone or desktop like a native app — no App Store, no Play Store, no review process. For internal tools and early-stage products this is a major advantage: faster to build, cheaper to maintain, and works on any device. All three of my live apps (CleanStock, MedShelf, ColdStock) are PWAs.

Where are you based and do you work remotely? +

Based in Palanga, Lithuania. I work fully remotely with clients across Europe and beyond. Communication is in English or Lithuanian. Time zone is EET/EEST (UTC+2/+3).

// Let's work together

Have a workflow, spreadsheet or product idea that should become a tool?

I turn messy processes into usable digital systems. If you have something that needs structure — let's talk about what that could look like.

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