"Not all those who wander are lost."

Hi! I'm Lincoln G. Santos, aka darkanum. I've been building things with technology since 2003: Ragnarok Online servers, training simulators, mobile games, payment rails for a digital bank, and now AI agents that review, fix and watch production code on their own. 🧭

Today I'm a Founding AI Engineer @ CoGrader and the founder of VapuLab, a software lab that builds B2B products.

• 📈 2M → 15M+ customers at Neon while I led the payments tribe tech (Boleto, Pix Cobrança, card acquiring, CDB)
• ⚡ Pix from day one (Nov 2020) to Pix Cobrança for businesses, on a platform moving US$1B+/month
• 🧾 1M+ downloads and 700k+ active users at MEI Fácil, from day one to the acquisition by Neon
• 🏆 Microsoft Imagine Cup 2013 winner in Brazil with InsuOnline, a diabetes training game for doctors
• 🎮 160k+ downloads on the games I shipped with my own studio, Red Stomp
• 🍎 100k+ teachers at 16k+ schools use the AI grading I help build at CoGrader

VapuLab

Logic. Infrastructure. Perception.

My company. A software engineering lab that builds B2B systems that have to be right: fast, auditable and hard to break.

Issue, copy and cancel Brazilian service invoices (NFS-e) through the national system. Multi-company, syncs your full history and never issues twice. notaflow.vapulab.com

Open-source design system in Go: 71 server-rendered components with templ, Tailwind and Alpine, ready for HTMX. Vapulab/malphas

AI grading for teachers, trusted by 100,000+ teachers at 16,000+ schools across all 50 US states, with 2.5M+ essays graded.

• ✍️ Build the AI grading pipeline: multi-file submissions, grammar feedback and exports back to Google Classroom
• 🦾 Created the AI agents that run engineering on autopilot: one reviews every PR, one turns bug reports into fix PRs, and one patrols production and sends each issue to the engineer who knows the code best
• ☁️ Designed the infrastructure those agents run on, on Azure

• 🧾 Built and runs NotaFlow, the lab's first commercial product, and the open-source malphas design system

• 💳 Channels squad and the payments engine that serves every interface of the company

• 📈 Led the payments tribe tech while Neon grew from 2M to 15M+ customers: Boleto, Pix Cobrança, card acquiring and CDB
• ⚡ On Pix from launch day, then took it from person-to-person to business collection with dynamic QR codes
• 🏛️ Built the platform for Neon's own-issued CDB (daily liquidity, up to 113% of CDI) after the Biorc acquisition

• 🚀 Joined on day one and helped build the app that lets anyone open and run a MEI from their phone: CNPJ, invoices, tax guides and boletos
• 📈 1M+ downloads and 700k+ active users in under two years, until the acquisition by Neon in 2019

• 🥷 Elemental Ninja: 100k+ downloads on Google Play
• 🐟 Farting Fishes: 60k+ downloads

• 🏆 InsuOnline: a game that trains doctors to diagnose and treat diabetes. Microsoft Imagine Cup 2013 winner in Brazil (World Citizenship) and world finalist in St. Petersburg, later proven effective in a randomized controlled trial
• 🕹️ Training simulators for Stara, Case and New Holland, plus a lot of minigames

• 🎓 Computer Engineering
• 🎓 Specialization in Game Development
• 🎓 Master's in Public Management, focused on technology

GitHub Stats

• IlluminaRO: I ran a Ragnarok Online server with 5k+ players. That's where it all started
• I went from playing games to making them, and I still play a lot

• I play in a rock/metal band
• I was also the sound designer of my own game studio

• Robotics: I love making hardware talk to software (ESP32 is my playground)
• Philosophy: always asking why before asking how

Support My Work

If something I built helped you, you can support it here. 💜

_{🇧🇷 Pix · any amount · VapuLab}