A well done & free four-chapter campaign/mod developed from 2005-2007 which utilizes Half Life 2 resources. The difficulty is very high (even on Normal) but can be excused with an abundance of ammo and no quicksave penalty. While this island seems small on the outside: you are left to "infiltrate and observe" at your own pace. Storyline is presented well although predictable. Several multiple-path scenarios, some decent puzzle solving, lots of high tension encounters, and plenty of baddies keep things interesting.
My only complaint is that most baddies take more than a clip to kill while all weapons have poor accuracy. Rushing & spraying most enemies can get frustrating. Perfect length for a campaign, which was about 5.5 hours while taking my time. Music is done well and used to bring tension.