How Algorium works
Algorium turns Codeforces into a head-to-head game. You pick the rules, we pick problems neither player has solved, and the scoreboard updates itself by watching your public submissions.
The loop
- 1. Sign in. Prove you own your Codeforces handle by submitting deliberately broken code to an assigned problem. We look for the compilation error — only the real account owner can produce one.
- 2. Host or join. Configure a room and share the 6-character code, or make it public and let anyone join from the home page.
- 3. Solve on Codeforces. Problems open there as normal. Submit with your own account.
- 4. Watch the board. Verdicts are picked up within seconds and pushed live to both players.
Game modes
Lockout
Every problem is open from the start. The first accepted solution claims that problem permanently — your opponent can no longer score it.
Best for: a broad race where you can cherry-pick what you're good at.
Blitz
A strictly linear race. Only the current problem is available; solving it locks it and opens the next one for both players.
Best for: fast, tense games where speed matters more than breadth.
Classic
Both players can solve everything. Most problems solved wins, with penalty time breaking ties — standard ICPC rules.
Best for: a fair test of total output over the full duration.
Scoring
Your score is the number of problems solved. Penalty time is the minutes elapsed at each solve, plus 20 minutes for every wrong submission that came before it. Lower penalty wins ties.
Problems are worth 100, 200, 300… by position, so the harder later problems are worth chasing. Penalty time still breaks ties.
Tie-breaks, in order: primary score, then total penalty, then whoever finished their last accepted solution earliest. If everything ties, it's a draw.
Rooms & formats
Play
You host and compete. The first person to join is your opponent.
Supervise
You host but don't play. The first two people to join are the contestants — useful for club matches.
Practice
A solo timed run against the clock. Nothing is rated and no match history is recorded.
Toggle list in open duels to publish your room on the home page so strangers can join. Leave it off and only people with the code can get in.
Camera & microphone
When you create a duel you can require contestants to keep their camera on, their microphone on, or both. Rooms with a requirement are badged in the open-duels list, so nobody joins one by surprise.
Before the start
Everyone runs a device check in the lobby. The host can't start until every contestant's devices are actually live.
During
Video sits beside the scoreboard. If a required device goes off, the problems are hidden and a countdown starts.
If it stays off
Past the grace period the host's choice applies — either the incident is logged and announced, or the duel is forfeited.
What this is, and isn't
A camera shows who is at the keyboard. It can't see a second device off to the side, so treat it as presence and accountability rather than proof of a clean match. Nothing is recorded — the video is live only, and the log afterwards shows how long each device was off, not what anyone did.
Supervisors are exempt: they're watching, not competing. Practice runs can't require anything, since there's nobody on the other side.
Series & rematches
When you host, you can make it a best of 3 or 5. Each game is its own room with a fresh problem set; the series score follows you across them and the first player to take the majority wins it.
After any duel, either player can hit Rematch. That creates a new room with identical settings and new problems, and sends the other player an invite. Inside a series, Rematch becomes Play next game.
Elo ladder
Every rated duel moves your Algorium Elo. It starts at 1200 and is completely separate from your Codeforces rating — beating someone stronger than you is worth more than beating someone weaker.
Your first ten duels are provisional and move the number faster while it finds your level. Resigning counts as a loss. Solo practice never affects it.