About
CS Nerd turns real pro Counter-Strike 2 rounds into puzzles. Every situation happened in a pro match: you read it, make your call, then watch what the pros actually did.
How it works
Each puzzle is a moment from a pro demo, frozen at the decisive point: a clutch, a retake, a buy decision or a hidden player. You answer, then the real round plays out on the radar.
There are three modes. Who wins?: call CT or T. Find the player: place the one nobody has seen. Buy call: eco, force or full buy. The daily set gives everyone the same five puzzles each day.
Your CS IQ
CS IQ is your rating. It uses Glicko-2, the system Lichess uses for chess puzzles: every rated answer is a game between you and the puzzle, and both ratings move. New players start at 1500, and a "?" means the rating is still settling.
Where the puzzles come from
Matches come from HLTV demos in the OpenCS2 dataset (CC BY 4.0), currently top-tier 2026 events such as IEM Rio, PGL Bucharest and BetBoom Mayhem. Moments are picked automatically from the demo data, and the answer is always what really happened.
Radar images come from awpy. Weapon and utility icons are drawn for this site, not taken from the game.
Free, no sign-up
You can play without an account. Your progress is tied to a random ID on this device, and the privacy policy lists exactly what is stored.
Signing in with Steam is optional. It keeps your CS IQ on every device you sign in on and puts your Steam name on the leaderboard. CS Nerd never sees your Steam password.
Not affiliated with Valve
CS Nerd is an independent project. It is not affiliated with or endorsed by Valve Corporation. Counter-Strike is a trademark of Valve Corporation.
Questions
- Is CS Nerd free?
- Yes. Every mode is free to play in the browser, with no account and nothing to download.
- Do I need an account?
- No. You can play without one. Signing in with Steam is optional: it keeps your CS IQ on every device and shows your Steam name on the leaderboard.
- Do I need Counter-Strike 2 installed?
- No. Everything runs on the site: each round is redrawn on a 2D radar from the match demo.
- How is the right answer decided?
- By what happened in the pro match. The puzzle freezes the round, and the real round, which you watch after answering, is the answer.
- When do the daily puzzles change?
- Every day at 00:00 UTC. Everyone gets the same five puzzles that day, so you can compare scores and keep a streak going.
- Does it work on a phone?
- Yes. The site is built for phones first and runs in any modern browser.