define TAU for older rust versions
use derive_more::{Add, Div, From, Mul, Sub};
-use std::f64::consts::{PI, TAU};
+use std::f64::consts::PI;
+
+pub const TAU: f64 = 6.283_185_307_179_586_f64;
/// The OrbTk way to handle angles
#[derive(Add, Sub, Copy, From, Clone, Debug, PartialEq, Mul, Div)]
