Because Apple maintains a strict "Walled Garden" approach to software distribution, users cannot simply download an IPA from a website and double-click to install it (unless they jailbreak their device). The IPA must be "signed" with a valid Apple developer certificate to run on a non-jailbroken device.
that mimic the classic PC experience.
on Apple mobile devices like the iPhone or iPad . While there is no official mobile version from Valve, the community has developed several "ports" and wrappers to bring the classic tactical shooter to iOS. Current Ways to Play cs 16 ipa new