Enable player to get energy drop several times

Now the player is able to get the energy drop more than one time.
Maintain state when getting several energy drops

Make the drop stay in the energy state after getting the energy drop
several times. Previously, the drop switches back to the normal state,
even after getting the energy drop.
Fix camera movement when player is inside straw

Make the movement of the camera smoother when the player is inside the
straw. It uses the FPS to calculate how much the camera should move.
This approach works fine when the FPS is about 60. When the FPS is low,
the camera movement is not so smooth, but it is much better than the
previous solution.