func (a Axis) String() string {
	if a == X {
		return "x"
	} else if a == Y {
		return "y"
	}
	return "z"
}
String converts an Axis into either x, y or z, depending on which axis it is.
package cube
import (
	"fmt"
)
type Axis int
const (
	Y Axis = iota
	Z
	X
)