Bejeweled 2

What causes the levels to change in the "Action" mode--is it certain number of points within a time period????
Just don't understand why Level 3 can be 38,000 or 138,000 before changing to level 4--just curious

it is so easy in www.ourworld.com .
just search the site you will see

omg...I am totally addicted to this game...and the highest level I have got to 8..has anyone got past 10..its hard too do! The timer goes quickly so you really have to hurry!