Two extremely popular Valve PC games, Portal and Half-Life 2 are now available on the NVIDIA Shield mobile gaming system, which is powered by an Android platform.

Released less than a year ago, the Shield has had its up and downs, however adding two such popular titles to its ever expanding library has increased its creditability.

Now they join a line-up that includes Titanfall, Batman: Arcane Origins and Elder Scrolls V: Skyrim.

Critics of the gaming device say that it’s too big and heavy to be considered truly mobile, but supporters herald its visual appeal, playability and functionality.

NVIDIA set out to create a mobile gaming device that would give a PC quality playing experience and even allow the streaming of PC games over a network, allowing multiple users to play together.

The Shield has recently lowered its price from $299 to $199, putting it in line with similar devices currently on the market.