Guitar_Scale_Length_mm = 648;
ln2 = ln(2);
function log2(x) = ln(x)/ln2;
function fret_scale_length(n) = Guitar_Scale_Length_mm * 2^(-n/12);
function mm_to_fret_number(mm) = -log2(mm/Guitar_Scale_Length_mm)*12;
function lerp(start, end, amount) = start + (end-start)*amount;