Flash distinguishes tweened animation from frame-by-frame animation in the Timeline as follows:
A black dot at the beginning keyframe indicates motion tweens; a black arrow with a light blue background indicates intermediate tweened frames.

A black dot at the beginning keyframe indicates shape tweens; a black arrow with a light green background indicates intermediate frames.

A dashed line indicates that the tween is broken or incomplete, such as when the final keyframe is missing.

A black dot indicates a single keyframe. Light gray frames after a single keyframe contain the same content with no changes and have a black line with a hollow rectangle at the last frame of the span.

A small a indicates that the frame is assigned a frame action with the Actions panel.

A red flag indicates that the frame contains a label.

A green double slash indicates that the frame contains a comment.

A gold anchor indicates that the frame is a named anchor.

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