Ok a brief overview on how to get it working with NVDA:
When the page loads, unless yo uhave something along the lines of firefox's addblocker, you'll receive an advertisement. Wait for it to end. After that, the game's main flash object is enabled.
Move to the heading that has the name of the game, your looking for the very first flash object after that. To jump to this in nvda, at the heading press O.
Once the flash object is selected. You'll hear "pane", use nvda's object review to open the list of child objects for said pane (nvda shift down arrow) for laptop. Once done, move through the objects with the appropriate gestures until you see the button that says "click here to play". Route the mouse to the button with nvda shift m for laptop, or the appropriate gesture for a desktop layout. I suggest reading your NVDA key guide or manual for any appropriate key gestures. After this a left click in any form will activate it. Saddly you can't skip over the cutsceen that follows.
The main menu:
The buttons are in order, left to right ignoring the graphics: Story Mode, Survival, credits, and some weird score/achievement thing. To activate any of these the process is achieved in the exact same way.
After selecting story mode, the button for each level is random. This is due to the fact that visually the levels are layed out in a certain way. Within this dialog however, tabbing will shift the focus to the button you are tabbed over. So you can tab, route mouse, then left click. This process repeats after completing each level. It is annoying, but at most it takes a few seconds to find the appropriate button.
The actual game
During the game, you are stationary and can rotate 360 degrees. Enemies will attack you from any angle. Obviously the enemies need to be nearly centered to defend or attack. The game is somewhat realistic about that, as you have leeway of about 10 degrees or so. Though the realism falls apart after you knock arrows out of mid air
and take on an army of men single handedly. As has been mentioned above the down arrow blocks or parries, where as the up arrow attacks.
Deep in the human unconscious is a pervasive need for a logical universe that makes sense. But the real universe is always one step beyond logic.