Draw: pick a shape and click the canvas to place it; for arrows, ropes, springs and lines, drag from start to end. Select to move things; drag the round handle to rotate and the square handle to resize. Delete removes, Ctrl/⌘ Z undoes, Ctrl/⌘ D duplicates. Labels accept m_1 (subscript), x^2 (superscript) and \vec{F} (arrow on top).