Windows ProblemsXyphr uses the system's internal clock for various timing purposes. Windows 3.0 (and probably other environments) alters the speed of this internal clock, thus, Xyphr should not be run under Windows. It won't cause any harm, but it WILL make the game unplayable on fast computers.
Source: The game's documentation
Xyphr was 10% written in C, the other 90% was in Assembly.