gasspring.app

Scroll to zoom and middle-click-drag (or hold Space and drag, or use two fingers) to pan — these work in every tool, including while calibrating. Drag a mount-polygon point to move it, and shift-click or ctrl-click it to remove it — works both in the normal Pan/zoom/drag mode and in Draw mount polygon mode (which is only needed for adding new points). In Calibrate mode, click two points a known distance apart — a line follows your cursor, then enter the real distance in the panel that appears. Save writes the whole board (including photos) to a file; Load brings it back.