When I first started the game, at single player I saw something really interesting at the single player tab: Challenges. It was a new feature for the game (among many others...), which made the single play more intense. Besides the 29 missions campaign, Blizzard offered us another 9 distinct missions, without any relevance to the story. The only things you get from these are some achievements you can brag about to the Bnet community with. Or so I thought...
The main purpose of them is really another: these challenges helps you understand all the new units, how to combine them when you attack, how to counter when you defend, how to make a time push, how to micro your units in order to survive with a small amount of life, and so on. It just helps you get a grip on the game and to enhance your abilities.
I strongly recommend everyone to start playing Starcraft 2 by completing the challenges first!
I tried to do the challenges a couple of times and all I could do was to get the silver medal. It was exciting to feel the difficulty but also frustrating because I tried numerous variations and still I was not good enough. I think of myself as a casual player rather then a pro, but it seemed too hard for me. So I started to watch different videos on the net with the challenges and found that you can finish them flawless, with 0 losses or killing everything on the map! And you don't have to be a pro to do it...
Thanks to NextGenTactics.com, I offer you gold rank videos for Starcraft 2 challenges.
Challenge 1: Tactical Command (0 Units Lost)
Challenge 1: Tactical Command (0 Units Lost)
Challenge 2: Path of Ascension (0 Units Lost)
Challenge 3: For the Swarm(0 Units Lost)
The advanced challenges are supplied by Psistarcraft, who did a great job in presenting us the way to victory.
Challenge 4: Covert Ops(Gold)
Challenge 5: Psionic Assault(Gold)
Challenge 6: Infestation(Gold)
The expert challenges are best explained by NextGenTactics.com, even though the commentary is not so good. But that's not so important because the footage will give you very good insight of what to do.
Challenge 7: Harbringer of Death(Flawless)
Challenge 8: Opening Gambit(Flawless)
Challenge 9: Opening Gambit(Flawless)