Counter Strike Online is a Counter-Strike game targeted towards Asia's gaming market. It is developed by Nexon Corporation of South Korea with oversight from license-holder Valve Corporation. It uses a micropayment model that is managed by a custom version of the Steam back-end.
People often overlook this just because its a pay-to-win. The zombies in this game are great and it allows for challenging gameplay. The graphics are Condition Zero graphics which are a bit aged. The pay-to-win isn't that bad in this game, most weapons can be bought and kept for about 1 - 30 days. I recommend you play this game for the zombies and PvP.