I'm amazed you could find
OoA. I have
OoS but have never been able to find
OoA 
__________________
"You're right, Half-Life 1 is the God of FPSs. Half-Life: Opposing Force is the holy ghost of FPSs, (Seriously, the holy ghost is really ****ing awesome, but no one EVER talks about it.) and Half-Life 2 is Jesus. (He's pretty cool, and can walk on water and ****, but he can't blow up cities on command like God can, so he's not quite as cool, and yet EVERYONE THINKS HES THE BEST. WTF?)" ~8bit