Product notes
Product updates, new challenges, and improvements, newest first.
Build your own DNS Server enters beta
Implement DNS packets, questions, and answers in a new challenge that launched in beta.
Experimental language guides
An early AI-guidance experiment reached learners, then returned to staff-only access in February 2024.
A Rust primer for experienced programmers
Work through interactive concepts covering Rust variables, types, control flow, and ownership.
Language setup guides
Language-specific setup documentation helped learners prepare their development environment.
Custom dependencies
Challenge implementations gained support for custom dependencies.
Build your own HTTP Server
Build a TCP server that parses HTTP requests and returns responses, using your own language and tools.
Build your own BitTorrent
Implement torrent metadata parsing, peer discovery, and file downloads in your own BitTorrent client.
More challenges in JavaScript and C++
JavaScript and C++ support expanded across the challenge catalog.
Redis gets RDB persistence
Go beyond an in-memory server: read RDB snapshots and restore persisted keys in the Redis challenge.
Challenge screencasts
The now-retired Screencasts tab introduced developer walkthroughs alongside challenges.
Achievement badges
A soft launch introduced badges for challenge progress. The dedicated tab was later retired in August 2025.
Interactive concepts
A soft launch introduced short, interactive lessons on topics such as network protocols and TCP.
Reading is good.
Doing is better.
Build your own Claude Code, Shell, or SQLite. Understand what’s underneath.