+ // precalculated tile positions
+ // assign x/y coordinates to each tile index
+ // looks dumb but is faster than on the fly isometric calculations
+ const dx = [], dy = [];
+ for ( let y = 0; y < h; y++ ) for ( let x = 0; x < w; x++ ) {
+ dx[y * w + x] = (w + x - y) * tw / 2;
+ dy[y * w + x] = (x + y) * th / 2;
+ }
+
+ // tile index for pixel position on map