I never saw the movie. Picked the game on on a friends recommendation, and have not looked back...
If anyone played King Aurthur's Castle on SNES back in the day, it is very very similar. Instead of attacking, you will be defending with some tower defense elements.
Basic idea is enemies come on right side, you defend left side. For defense you have castle attackers (which you don't start with, you buy and upgrade), yourself and then your troops. The blacksmith builds your bricksmoney whatever that you use to build troops, which start on the left side and walk to the enemies and fight.
Simple, but there are little things you do to make it interesting. Better troops cost more of course, but if you wait long periods of time for troops, you have 1 guy fighting 3 guys. Blacksmiths can be upgraded to give faster bricks, but at to cost of buying bricks now.
Bricks and coins are dropped by enemies. Coins are used for upgrades in between rounds. You can upgrade the castle and defenses, your troops healthdamage, or yourself.
You are the best fighter. You just really select walk left or right. You pick up dropped items. If you die, game over, try wave again. You also have 2 special attacks. You get to pick 5 troops and 2 special attacks per round, with a selection of about 20 and 6 respectively.
Those are the basics. And it is fun enough to play for 3 hours, which should be enough to feel like you got your $ worth. I think I will play this 10+ hours myself.