Just when Rollercoaster Tycoon couldn't get any better, Chris Sawyer released the second in the series and lo, it was! Simply one of the greatest simulation games ever devised, RT2 is a challenging, relaxing and above all fun way to blitz through the days/weeks/months etc... And unlike other versions out there, this one works on Windows 7 in 64bit. Hurrah! Awesome.
Total Annihilation. The greatest RTS ever. The end.
