Your first reel

A reel is a text file ending in .reel. The smallest one records an app's window for a few seconds:

Text 
# hello.reel
Launch com.apple.TextEdit
Output hello.mp4
Sleep 3s
Shell 
reel hello.reel

reel opens TextEdit, waits for its window, records it for three seconds and writes hello.mp4 next to the reel. The recording itself, the take, is kept in .reel/hello/, so changing what is drawn over it doesn't need a new recording.

Text 
Launch com.apple.TextEdit
Output hello.mp4
Output hello.gif
Set Size 1200x800

Key cmd+n
Caption "A new document"
Type "Written by a reel.\n"
Key cmd+a
Sleep 1s
  • Set Size sizes the window before recording starts.
  • Key cmd+n presses the keys; a badge shows ⌘N in the video.
  • Caption shows text along the bottom from that point on.
  • Type types a character at a time; \n is return.
  • Output hello.gif writes a GIF as well, from the same recording.

reel check hello.reel reads the reel and says what it would do, without recording anything.

Text 
Set Voice system
Say "TextEdit opens a new document."
Key cmd+n
Say@over "Then we type [type] a line."
Wait [type]
Type "Written by a reel.\n"

Say speaks a line in macOS's voice and waits for it to finish. Say@over speaks and carries on, and Wait [type] waits until the voice reaches the [type] marker, so the typing starts on that word. See Narration.

Captions, narration placement, zooms on a point, speed-ups, cuts, title cards and every output setting are applied when rendering. Edit them, then:

Shell 
reel render hello.reel

Only a change to what happens in the app (a click, typed text, a spoken line) needs reel hello.reel again.