axial-coordinates.js

/**
Axial coordinates

# convert cube to axial
q = x
r = z

# convert axial to cube
x = q
z = r
y = -x-z

# convert cube to even-q offset
q = x
r = z + (x + x&1) / 2

# convert even-q offset to cube
x = q
z = r - (q + q&1) / 2
y = -x-z

# convert cube to odd-q offset
q = x
r = z + (x - x&1) / 2

# convert odd-q offset to cube
x = q
z = r - (q - q&1) / 2
y = -x-z

# convert cube to even-r offset
q = x + (z + z&1) / 2
r = z

# convert even-r offset to cube
x = q - (r + r&1) / 2
z = r
y = -x-z

# convert cube to odd-r offset
q = x + (z - z&1) / 2
r = z

# convert odd-r offset to cube
x = q - (r - r&1) / 2
z = r
y = -x-z

**/

export function cubeToAxial(x, z) {
  return { q: x, r: z };
}

export function axialToCube(q, r) {
  return { x: q z: r y: -q - r };
}