Level 11
Level 11, "The Descent into the Underworld" is similar in many ways to the previous world, "Uraeus Nefertari"; both feature difficult horizontal straits that traverse the entirety of the play-field leading directly to the pyramid end-goal. However, a new challenge appears in this world in the form of bridge-like obstacles that the chain of puzzles spheres must pass under on their path to the pyramid. Any spheres shot at these bridges will pass over the chain below the bridge and hit the higher layer of spheres instead. With this new level of challenge, you'll need to be careful never to shoot for the chain while it is located under the bridge or your sphere will fail to connect.
You can occasionally use the bridges to your advantage if you see a group of blocks heading over the bridge that matches the color of your sphere. If you can carefully time and aim your shot, the sphere will pass over the bridge and meet the group of spheres as they approach the bridge.
This world rewards quick thinking and will punish you if you take too much time trying to build large combos. You can become quickly overrun by the growing chain of spheres on such long, serpentine trails, so it is recommended that you try to destroy chains as soon as they appear on screen. This will help keep the overall length of the chain manageable and easily solved.
General Tips
Many stages in level 11 feature sharp, snakelike curves where the chain moves back in on itself. These curves are important as they can be easily exploited by the various power ups available. Fireballs, which destroy a large group of spheres, can be shot toward the chain as it approaches a curve to hit both sides of the chain. Even more valuable is the lightning power up, which destroys spheres in a straight line. Aiming the lighting up the edge of the parallel curves will allow you to strike a huge number of spheres once the chain has progressed far enough along its path.
Beating Khufu
Khufu's Revenge is the boss of level 11 and one of the most difficult stages in the game. There is no surefire way to beat this level on a first attempt, so be certain to practice it multiple times if you are having difficulty beating it. There are a number of things to take into consideration, which may make the fight a bit easier.
Try to save your lightning power ups on this level until you have a large chain filling up the right hand column of the level. This section of the level is the most vulnerable to lightning attacks, and a well placed one will make the level far easier to complete. Similarly, save up your fireball attacks for near-death scenarios where they can provide sudden relief and a second chance at clearing the chain.
Keep the chains from entering the tunnel area on the map. This is the most important part to beating the level. Once the chain has entered the tunnel, you will be unable to interact with it until it comes out on the other end, dangerously close to the pyramid. Constantly clear even the smallest matches leading up to the tunnel, and always keep an eye on the end of the chain. If you can keep the chain from reaching the tunnel until the very end of the match, you will have a much easier time completing the level.