If you're having trouble finding the official download link, you can try:

If you specifically want a classic, lightweight version reminiscent of "CS 1.6" (which some modders incorrectly label as CS 18), your safest bet is to play CS2 on classic community servers or buy Counter-Strike: Condition Zero from authorized key resellers.

is essentially a "greatest hits" overhaul of the classic 1.6 engine. It attempts to modernize the 2000s-era gameplay by porting visuals, weapons, and menus from newer titles like Global Offensive into the lightweight GoldSrc engine. Visuals & Sound:

: Features a streamlined menu for quick installation and navigation. Flexible Play Modes