I think instead of storing coordinates, you would be better off storing directions (with great approximation (range) allowing for an offset on the y coord – can’t expect the player to draw something exactly in the heat of battle) and measure the length of directions when the direction changes.

Above a minimum size, any size glyph could be accepted – so it is independent of drawn glyph sizes, but more importantly – screen resolutions.

Good luck! This topic looks really interesting, I’m looking forward to your next GG blog!