Yellow Sun Systems

Superpowers for everyday people.

We build focused, thoughtful apps that help ordinary people do extraordinary things — tools that feel like superpowers.

Planning & Decisions

Monaco

Monte Carlo retirement scenario analysis. Enter your plan (with a guided Interview mode), run thousands of trials, get plain-English answers to the big questions — including the “widow tax” when a spouse passes — then explore the full results.

  • Four-tab flow: Plan Input → Run Simulation → Answers → Explore Results
  • Interview mode walks every field with plain-language questions and defaults
  • Answers tab: Can I retire safely? When can I retire? Best Roth conversion? Best SS claim age?
  • Runs entirely in your browser — your data stays on your device
Learn More → Go to app

Retire Slider

A one-screen retirement planner. Type in your net worth, slide your annual spending, and watch your 30-year risk-of-ruin update live — Social Security, expense breakdown, and taxes all baked in, no simulation noise.

  • Closed-form reciprocal-gamma risk-of-ruin — instant, deterministic
  • Optional 25,000-path Monte Carlo cross-check
  • Expense breakdown with auto-estimated federal + state taxes
  • Shareable links — scenario travels in the URL, never on a server
Learn More → Go to app

House Ranker

A shortlist tool for house hunting. Paste a Zillow URL, and the app pulls the listing, scores every candidate on your customizable factors, and ranks them — with AI-generated reasons you can override any time.

  • Auto-extract details and photos from any Zillow listing
  • 13 built-in factors (weather, neighborhood, privacy, price, view…) — all editable
  • AI scores each factor with a plain-English reason; you can override any score
  • Photos auto-classified by room type: kitchen, backyard, view, and more
Learn More → Go to app

Creative Tools

DreamZone

A personal dream journal with AI-powered analysis. Capture your dreams, discover patterns, and unlock insights from your subconscious mind.

  • Record and search your dreams
  • AI-powered dream analysis
  • Track mood trends over time
Learn More → Go to app

The Writing Sessions

A focused creative writing tool designed to help you build a consistent writing habit and push past the blank page.

  • Timed writing sessions
  • Distraction-free environment
  • Track your writing streaks
Learn More → Go to app

Quill

⚗ Prototype

An AI-centric spreadsheet with a flexible canvas — floating rich docs, images, shapes, slides, slide decks, and reusable grid snippets all in one place.

  • Spreadsheet grid plus floating rich docs
  • Images, shapes, slides, and full slide decks
  • Reusable grid snippets for dashboards and templates
Learn More → Go to app

Health & Fitness

Step Right

An iPhone step tracker that turns walking into a game. Set a goal, watch the ring fill, keep your streak alive, and get a burst of confetti the moment you cross the finish line — powered by Apple Health, no logging required. Free, with no ads.

  • Free to use — no ads, no sign-up
  • Animated Today ring with distance, calories, and goal %
  • Streaks, milestones, and playful vibe status labels
  • Weekly and monthly trend charts with best-day highlights
  • Reads Apple Health data locally — nothing leaves your device
Learn More → Available on the App Store

Games

Dungeon Crawler Lucas

⚗ Proof of Concept

A multi-level dungeon survival game where a hero and friends must work together against creatures and magic — guided by The Announcer as they fight toward an uncertain freedom.

  • Multi-level dungeon progression
  • Hero and party cooperative survival
  • Narrated by The Announcer
Learn More → Go to app

Solitaire

A clean, classic Klondike solitaire you can play right in your browser — no ads, no sign-up, just the cards.

  • Classic Klondike gameplay
  • Coach Mode to help sharpen your playing skills
  • Plays instantly in your browser
Learn More → Go to app

Also available for iPhone on the App Store.