"Replaying" appears in the status text when previously-performed actions will be performed again automatically. "Replaying" can be cancelled by performing an action or by clicking the left mouse button (or touching) in the level viewport.
Holding down the right mouse button changes the selection algorithm.
Playing with touch controls works, but a mouse is recommended.
Touching with two or three fingers performs fast/step backward/forward depending on which half of the screen is touched.