function hexRing(center, radius) {
let results = [];
if( radius === 0) {
results.push( center);
} else {
const dir4 = hexgrid.Hex.direction(4);
let hex = center.add( dir4.scale( radius));
for( let i = 0; i < 6; i++) {
for( let j = 0; j < radius; j++) {
results.push( hex);
hex = hex.neighbor( i);
}
}
}
return results;
}