Practice

Write Common, press Run, see what the visitor would see. Nothing you type can touch the server.

GoalFinish the sentence with the math inside brackets, so it says: Total: 13.5
Add:
Hint
Math can go inside the brackets too, and multiply is *. After three tries the full answer appears.
Press Run to see the result here.
The three rules, and that is all of them
  1. Every line starts with a command: show, set, if, for each, repeat…
  2. A value goes inside text in brackets: show "Hello, [name]"
  3. if, for each, repeat, to, and a show on its own, own the lines below them, up to a line that says end.
How this page runs your code safely
set program to form "code"
set result to try program
if result contains "Hello, World!"
  show "✓ That does it."
end

try runs text as Common with files, the database, cookies and redirects switched off, and stops after 20,000 steps or 64 MB of memory. The result is shown inside a sandboxed frame, so even HTML you write stays inside its box.