uwyudai@gmail.com
Senior Fintech Engineer
Hello, my name is

Yudai Yaguchi

Senior Software Engineer

Guided by a desire to craft technology with purpose, I am dedicated to learning and applying my full-stack development skills to create solutions that benefit people and communities. Enthusiastic about the transformative potential of machine learning, I aspire to blend my technical knowledge with innovative ideas to deliver impactful digital experiences.

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Yudai Yaguchi

Featured Work

Selected projects that blend product thinking, clean code, and practical impact.

Useful Tools

Production-ready utilities built to solve real-world day-to-day problems.

SettliSettlement Tool

Smart group payment settlement. Automatically finds the optimal transfer plan for complex bill splits.

Optimized SettlementWeighted SplitQR Share

KaimonoShopping List

Smart shopping lists with budgets, categories, sharing, and recurring item reminders.

Budget TrackingRecurring ItemsQR Share

KuizuQuiz Tool

Multiplayer quiz platform with 400+ questions, daily challenges, custom quizzes, and live scoreboards.

Multiplayer RoomsDaily ChallengesCustom Quizzes

MD PreviewMarkdown Viewer

Drag & drop or paste markdown files for instant full-screen preview with GitHub Flavored Markdown support.

Drag & DropClipboard PasteGFM Support

TodoAI Task Manager

Extract tasks from screenshots or text with AI. Manage your todo list with smart input.

Screenshot to tasksText extractionAI-powered

スコアトラッカーScore Tracker

麻雀の素点、ゴルフ、ボドゲ会など — 日付ごとの最終点を記録して累計を追跡。コードで友達と共有できます。

日次スコア記録累計の自動集計コード共有

Coming Soon...

More practical tools are on the way.

Interactive Games

Playable experiments focused on UX, performance, and game logic design.

Click to Play

Jump Game
Easy
A classic jump-and-dodge arcade game. Press any key to jump over obstacles and rack up points!
Arcade

Click to Play

Tic Tac Toe
Medium
Challenge the AI in this classic strategy game! Choose from Easy, Medium, or Hard difficulty and test your skills.
Strategy

Click to Play

Gomoku
Hard
Five in a Row! Strategic board game with AI using minimax and alpha-beta pruning. Can you outsmart the algorithm?
Strategy

Click to Play

Tetris
Medium
Classic block-stacking puzzle game. Clear lines by completing horizontal rows. Speed increases as you level up!
Puzzle

Click to Play

Shogi
Hard
Japanese Chess! Strategic board game with piece drops and promotions. Challenge the AI in this classic strategy game!
Strategy

Click to Play

Othello
Medium
Classic strategy board game with AI using alpha-beta search. Flip your opponent's discs to win!
Strategy

Click to Play

Mini Adventure
Hard
Roguelike dungeon crawler! Descend 10 floors, manage your torch, and defeat the Dragon boss!
RPG

Click to Play

Animal Roleplay Survival
Medium
Become an animal and survive 10 turns. Choose actions each turn to manage HP and hunger and reach the best score.
RPG

Click to Play

Breakout
Easy
Classic brick-breaking arcade game! Use your paddle to bounce the ball and destroy all bricks. Collect power-ups!
Arcade

Click to Play

Space Invaders
Medium
Defend Earth from alien invasion! Destroy waves of enemies, use shields for cover, and shoot the mystery UFO for bonus points.
Arcade

Click to Play

Daifugo
Medium
Play Daifugo (Rich Man Poor Man) vs AI (3-6 players) or online (3-6 players). Create a room, share the code, and battle to empty your hand first!
Card

Click to Play

Shichinarabe
Easy
Play Shichinarabe (Sevens) vs AI (3–6 players) or online (3–6 players). Build sequences around the 7s and be the first to empty your hand!
Card

Click to Play

Doubt
Medium
Play Doubt (Cheat/Bluff) vs AI (3–6 players) or online (3–6 players). Play cards face-down, claim the rank, and call Doubt to catch liars!
Card

Click to Play

Reverse Jump
Medium
Controls reverse every 8 seconds. Jump low obstacles and duck high bars to survive.
Arcade

Click to Play

Ghost Tetris
Hard
Locked blocks fade after 2 seconds. Remember the board and keep clearing lines.
Puzzle

Click to Play

Chaos Breakout
Hard
Breakout with chaos pulses: gravity, speed, and paddle size change every 10 seconds.
Arcade

Click to Play

Doubt Word
Medium
A bluff duel using claimed word initials and lengths. Believe or call Doubt.
Card

Click to Play

Timed Button
Easy
One button mind game: pass the bomb before the hidden timer explodes.
Arcade

Click to Play

Mirror Othello
Hard
An Othello variant where the board mirrors every 4 turns.
Strategy

Click to Play

Memory Maze
Medium
Memorize the maze quickly, then navigate to the goal in near darkness.
Puzzle

Click to Play

Daily One-Move Puzzle
Easy
A daily tic-tac-toe puzzle: find the winning move in one turn.
Puzzle

Click to Play

Bigger Number
Easy
Pick a tile, reveal at the same time as your opponent — higher number wins. Vs AI or 2-player online.
Card

Click to Play

Territory Number
Medium
A 3×3 territory game where number cards capture lines. Place 1–9 strategically — most lines wins.
Strategy

Click to Play

Memory Battle
Easy
Five cards flash for 3 seconds, then flip. Find the requested number to score before time runs out.
Puzzle

Click to Play

IQ Test
Medium
A short IQ-style quiz with procedurally generated questions: number sequences, odd-one-out, analogies, and more.
Puzzle

Click to Play

Roulette + Martingale Sim
Easy
European roulette you can actually play, plus a Monte Carlo simulator that shows how the Martingale strategy goes bust.
Arcade

Click to Play

Monty Hall
Easy
The classic three-door problem. Play it, then run a Monte Carlo simulation that shows Switch beats Stay 2:1.
Puzzle

Click to Play

Birthday Paradox
Easy
How few people do you need before two share a birthday? Play it, then simulate the famous 50% / 99% thresholds.
Puzzle

Click to Play

Coupon Collector
Easy
How many draws to collect all n items? The classic gacha problem: expected draws ≈ n·ln(n) — the last few items take forever.
Puzzle

Click to Play

Gambler's Ruin
Easy
Even with a fair 50/50 game, finite bankroll means ruin probability is (N − a) / N. Make it 49/51 and ruin becomes nearly certain.
Puzzle

Click to Play

Blackjack — Basic Strategy
Medium
Play simplified Blackjack with a hint that shows what Basic Strategy says. Then simulate it vs Mimic-Dealer vs Always-Stand and see the edge gap.
Card

Click to Play

Secretary Problem
Medium
Interview candidates one by one, decide on the spot, no second chances. Try beating the famous 37% rule — then simulate it.
Puzzle

Click to Play

K-armed Bandit
Medium
Explore vs exploit — pick arms with hidden reward probs. Compare ε-greedy, UCB1, and Thompson Sampling regret curves.
Puzzle

Click to Play

Bayesian Update
Medium
A coin with hidden bias. Flip and watch the Beta posterior sharpen around the true p in real time — then simulate convergence.
Puzzle

Click to Play

St. Petersburg Paradox
Medium
Coin flips until first tails: payoff doubles each round. Expected value is infinite — yet nobody wants to pay much. Simulate why.
Puzzle

Latest Blog

Notes on engineering, lessons learned, and ideas explored in public.

Coming soon...
about

Software Engineer

Yudai Yaguchi

Biography

Hi, I'm Yudai — a senior software engineer based in San Francisco with 6+ years building large-scale fintech systems. At Atlas and PayPal, I've owned the kind of work that quietly determines whether a fintech company stays solvent: payment rails, KYC/OFAC compliance, customer-support infrastructure, and the internal platforms operations teams rely on every day. I take complex initiatives end-to-end as the directly responsible individual — architecture, rollout, and the unglamorous edges that make production systems reliable. Outside of work, I lead an AI meetup community for engineers and keep exploring how machine learning fits into the everyday products people depend on. I'm pursuing an MS in Computer Science at Westcliff University while looking for the next role that blends deep engineering with cross-functional leadership.

  • 27 years
  • San Francisco, Remote
  • uwyudai@gmail.com
  • English, Japanese

Experience

Education