Challenge.gov is a collection of challenge and prize competitions, all of which are run by more than 50 agencies across federal government.
As a game, it is simply a collection of clever, challenging puzzles interspersed with mild action, equal parts Tomb Raider and Myst.
Case in point: South African artist Anelia Loubser's series "Alienation". "'Alienation' is a collection of portraits that challenges the viewer by using creative tactics based on the concept, 'If you change the way you look at things, the things you look at change,' [by Wayne Dyer]," Loubser writes in a statement supporting the work.
They have released a collection of photos that challenge these stereotypes and offer a more empowered vision of modern women and girls.
This weekend, for whatever reason was a collection of moments that challenged and changed me.
The label comes from her August 2014 book's title, a collection of essays which challenged how we define and interact with feminism.
Hence, as the preceding discussions show, Moore's legacy is primarily a collection of arguments, puzzles and challenges.
In a recent speech Hillary Clinton called climate change, "the most consequential, urgent, sweeping collection of challenges we face as a nation and a world".
Five years before Clarke began working on "2001," he published a collection of essays entitled "The Challenge of the Spaceship," in which, at the end, he pays a tribute to Homer: Across the gulf of centuries the blind smile of Homer is turned upon our age.
While declaring climate change the most "consequential, urgent, sweeping collection of challenges we face as a nation and a world", Clinton has faced suspicion from liberal elements in the party because of her close connections to the oil and gas industry.
