Notes:

• Also try BQNPAD, a third-party interactive REPL, and BQN Editor, which is basically this page but better. CBQN is the much faster offline interpreter (more options).
• The top bar has everything you need to know about BQN's special characters. Click to enter it, hover to see its name and the backslash combination you can type instead, and middle- or modified click to go to a help page.
• The code window is vertically resizeable.