There are a total of 13 challenges that each require you to find collectables. In each challenge there are 4-10 collectables. When you have completed Story mode you will enter Free Roam mode where you will be able to complete ALL of the challenges. The game will save automatically whenever you pick up one of the collectibles and once the challenge has bee successfully completed you will recieve the corresponding Achievement.
How trusted are this members submissions. Higher ratings are reached by having more submissions, being a pro submitter, a game expert and having good thumb ratings for sufficient submissions on the site.