Gabriel Castillo

CS Major @ Cornell

Gabriel Castillo

I'm Gabriel, a Computer Science major at Cornell University.

I have been learning to code since I was 12. Having started with learning Python to build simple programs to learning JavaScript to use React Native to build cross-platform mobile applications, I have spent the last 6 years falling more and more deeply in love with Computer Science. Currently, I am learning PyTorch and C++ to dive into AI and highly efficient algorithms. Besides that, I am developing some cross-platform mobile apps in order to launch a start-up.

During my free time I enjoy going to the gym, playing piano and listening to music.

Experience

Full-Stack Software Engineer Intern

rapStudy | US DoE-funded Musical Ed-Startup

Dec 2024 - Aug 2025 Remote

Refactored a 5,000+ line React codebase, improving page load times by 30%. Resolved major Firebase syncing issues and delivered 3 new features that enhanced platform usability.

React Firebase JavaScript Redux CSS3

FOCUS Fellow

Jane Street

May 2025 New York, NY

Completed market simulations and problem-solving challenges. Gained hands-on exposure to OCaml for quantitative finance and analyzed behavioral finance case studies.

OCaml JavaScript Redux

Full-Stack Software Engineer Intern

Blue Pond Group Ltd. | Hatch Blue Backed Startup

Aug 2022 - Jun 2024 Chiang Mai, Thailand

Built company website and developed an iOS app for shrimp farmers with 30+ beta users. Boosted profits by 15% through Python analysis and helped get company accepted to Hatch Blue.

Swift Firebase Python HTML CSS JavaScript

Projects

Harbor (Click Me!)
Cornell Connection App
Harbor app

Spearheaded full stack development with React Native (Expo), TypeScript, Firebase. Built secure photo reveal system with an intermediate consent screen using GCloud Storage Signed URLs. Implemented Cornell-only access with a custom email verification flow and strict @cornell.edu enforcement.

Frontend: React Native, Expo, TypeScript
Backend: Firebase, GCloud Storage

Odyssey
Interactive OCaml Theorem Prover
Odyssey theorem prover

Worked with 3 others to build propositional logic theorem prover with SAT solving and tautology check. Implemented recursive descent parser and AST interpreter in OCaml with 5 logical operators. Developed interactive CLI with ANSITerminal for colored output and step-by-step proof visualization.

Built With: OCaml, ANSITerminal
Features: CNF conversion, DIMACS export, LaTeX generation

LockedIn
Swipe-Based Professional Networking
LockedIn logo

Head frontend developer of LockedIn, an app lets users swipe to network, making professional connections effortless. Won best UI (out of 25 teams) in Cornell AppDev's Hack Challenge.


Frontend: Swift, UIKit
Backend: Python, Flask, SQLAlchemy, Docker, Firebase

Critter World
Evolving Artificial Life Simulator
LockedIn logo

Led a team of 4 to build a simulation where creatures evolve through eating, reproducing, and mutating. Designed a language parser, interpreter, and simulation engine with a GUI capable of running billions of ticks to model realistic evolution.

Built With: Java, JavaFX, Gradle
Cannot share code due to academic integrity reasons.

Kogyo
The Marketplace of the Gig-Economy
LockedIn logo

Built entirely by me, Kogyo, dubbed "The Uber of Tasks", is an app that effortlessly matches freelance labor (helpers) with customer requests (tasks). With the limitless task categories available any task is just one tap away.

Frontend: React Native, Expo Go, Typescript
Backend: Node.js, MongoDB

Sleek Devs
Premium Web Design & Development
Sleekdevs website

Founded a premium web design, development, and SEO services business to help businesses stand out online. Offering comprehensive solutions from custom domain setup to advanced SEO optimization. Built beautiful, high-performing websites with full hosting, maintenance, and support.

Services: Web Design, Development, SEO
Tech Stack: HTML, CSS, JavaScript, Bootstrap

Technical Skills

Languages
Swift

Swift

Java

Java

JavaScript

JavaScript

Python

Python

HTML

HTML

CSS

CSS

Frameworks
React

React

React Native

R Native

Node.js

Node.js

UIKit

UIKit

SwiftUI

SwiftUI

Bootstrap

Bootstrap

Tools
Git

Git

JUnit

JUnit

Docker

Docker

Postman

Postman

MongoDB

MongoDB

Firebase

Firebase