Concrete
AboutDownload
06 / 07

Sandbox

Run the example.

Run supported Python and JavaScript snippets in an isolated sandbox while you study. Output appears in the editor, under the code, and is not saved unless you want it.

Languages
Python · JavaScript · TypeScript
Runners
Docker or Daytona
Output
Inline, not persisted
Setup
Pick a runner in Settings
Physics / free-fall.md
python▶ Run
def falls(t, g=9.81):
    return 0.5 * g * t**2

for t in (1, 2, 3):
    print(t, round(falls(t), 2))
Output · 0.41s
1 4.91
2 19.62
3 44.15

Illustration in the Concrete theme

How it works

Three steps.

  1. 1

    Write

    Put a fenced code block in any note.

  2. 2

    Run

    Run it. The code executes in an isolated container, locally with Docker or remotely on Daytona.

  3. 3

    Iterate

    Change a parameter, run it again, and compare.

Why it matters

Safe by design

Snippets run in a container, away from your files and system, so a bad loop can't hurt anything.

Clean notes

Outputs aren't written to disk automatically, so your Markdown stays readable.

Pluggable runners

Runners are pluggable. Docker and Daytona ship today, and more backends can be added.

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Progress →

Scores, skills, and streaks over time.