Mastery challenges gone! Huge mistake!

I've used this program for 12 years since I taught AP calc and have outstanding results thx to Khan and its videos and practice. Finding out mastery challenges were removed was extremely disappointing and honestly make no sense. I had a 3 step model for my students to attack each lesson within.each unit and now its gone! Ridiculous! PUT IT BACK!!! People donate to your program and this.is how we are treated!