Learn to code for real.
A programming-learning platform where your code ships to an isolated container and faces real tests. Not a quiz, not a video.
Free to start · nothing to install · Windows, macOS and Linux if you prefer native
Try it right now, no account
CIPHER grades your code in a real isolated container, with no network. Write it, run it — three test cases you cannot see decide.
Objective
Return the sum of the packet's bytes, modulo 256.
Sealed cases
0/3- paquet_courtSealed
- debordementSealed
- double_maximumSealed
What you just did is the product. The same container, the same hidden tests, the same grading — across the whole catalogue. Nothing here is simulated.
Four grounds, one progression
Elsewhere, four separate products. Here a mission's XP unlocks a course and credits spend everywhere: progress in one place has consequences in another.
Missions
Challenges graded against real hidden test cases, from the plainest to the most demanding.
Academy
Structured tracks per language: lessons, examples, then derived exercises that climb.
Arena
Two players, the same brief, graded server-side. A rating that moves with every duel.
Playground
All eight languages, no brief and no grade. For trying an idea at three in the morning.
Everything feeds the same progression
Eight genuinely executable languages
Not eight logos: eight runtimes in the sandbox. If a language is here, your code runs in it.
- PYTHONtest runner
- JAVASCRIPTtest runner
- TYPESCRIPTtest runner
- RUSTtest runner
- GOtest runner
- JAVAtest runner
- KOTLINtest runner
- SQLstdin only
- PHPtest runner
A constraint we own: the container has no network, so it is standard library only. No mission assumes a downloaded package.
An academy, not a playlist
Ordered courses, lessons, and exercises graded by the same sandbox as the missions. You do not watch anything, you write.
Track → course → lesson → graded exercise
- 9
- tracks
- 31
- courses
- 205
- lessons
Projects, not fill-in-the-blank exercises
A file tree, not a function. Your code has to stand up to tests you will never see — the way it works in real life.
One real project per language with a test runner — Python, JavaScript, TypeScript, Rust, Go, Java, Kotlin — plus the warm-ups.
18 project missions
- Cargo.toml
- src/lib.rs
- src/trame.rs
- tests/decode.rshidden test suite
Progression is the product
What you earn stays, shows, and compares. A session that does not bring you back tomorrow is a failure.
- INITIATE
- OPERATOR
- SPECIALIST
- ENGINEER
- ARCHITECT
- CIPHER ELITE
Six ranks
From first access to the network all the way to elite. Rank is earned in XP and never lost.
Five divisions
A weekly league of twenty-five peers. The top five go up, the bottom five go down, and the division badge stays.
Verifiable certificates
A finished track issues a certificate with a public code. Anyone can verify it — a recruiter included.
Streaks and review
Spaced repetition brings back what you got wrong, right about when you have almost forgotten it.
Free to start
Not a demo in disguise: all four modes are in it.
Free
€0forever- All eight languages, across all four modes
- The full academy and its graded exercises
- Arena, leagues, certificates and streaks
- AI mentor — 5 questions a day
Pro
Price to be setnot on sale yet- AI mentor with no daily cap
- The missions marked as paid
- On-demand mission generation
We do not sell a Pro subscription yet, and we will not print a price we have not settled. The free tier, on the other hand, is complete and available now.
The native app, if you prefer
The web is enough to start. The installed app stays on your dock.
What people ask us
Yes, and you can check it above without creating an account. Every submission ships to an isolated Docker container, with no network, read-only, and faces test cases you cannot see. The verdict and the timing shown come from the server.
You have seen the only thing that matters.
The rest of the catalogue is graded exactly like what you just ran.
Launch the appFree to start · nothing to install