1. Click inside the window so your cursor disappears. This will allow you to look to the left or right as much as you want.
2. To bring your cursor back, press esc, and then you can move it back into the browser.
Controls are "WASD"
W is to walk forward (think up arrow)
A is to walk backwards (think down arrow)
S is to strafe left (move left while facing forward)
D is to strafe right (move right while facing forward)
Use mouse to control where you look at