There are 11 difficulty levels although reaching level 6 is very difficult. You start at level 0.
You start with 50 seconds, but every time you level up you get a bonus of 5 additional seconds. At level 8 you stop receiving that bonus. The bonus is only for humans.
A hit of points according to the following formula:
points = points for level + point for complexity
There are an infinite number of calculation tricks, but there are two keyboard tricks that help you to be faster: