OBFH Games
Games for nerds
Skill drills disguised as play. Everything here runs entirely in your browser, works with a keyboard, respects reduced-motion settings, and stores nothing beyond an optional personal best that never leaves your machine.
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In the cabinet
Placeholders, honestly labeled: these are designed and queued, not hidden behind a signup. They ship as they're finished.
Subnet Sprint
CIDR math against the clock: hosts per subnet, first usable address, does this IP live in that block? The mental arithmetic every network interview assumes you have.
Subnetting · Mental CIDR math
Phish or Legit?
Judgment reps on fully synthetic emails: headers, links, and tone. Call each one, then see the tells you caught — and the ones you missed.
Phishing detection · Header analysis
Regex Rescue
Pattern puzzles from real log-wrangling life: match the timestamps, capture the usernames, leave the noise. Difficulty ramps from \d to lookaheads.
Regular expressions · Log parsing