Practice

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

Scratchpad Lessons Exercises
Add:
Reset Glossary ↗
Hint
Things to try, one per line of thought: 
set fruits to "apple", "banana"
for each fruit in fruits
  show "<li>[fruit]</li>"
end

if the count of fruits is more than 1
  show "plural"
end

show "Today is [date of today]"
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.