Artemis makes use of all three buttons of the mouse under X, but other windowing systems often have less than three buttons. To make life easier when running Artemis on those systems, there are some alternative key bindings.
On Windows pressing the alt or meta key and the first mouse button will give the same effect as pressing mouse button three (usually a pop-up menu). Pressing the control key and the first mouse button will do the same thing as mouse button two.
On Macintosh systems pressing the control key and the mouse button will give the same effect as pressing mouse button three (usually a pop-up menu). Pressing the alt key and the mouse button will do the same thing as mouse button two.