Obamacare / 30 hour full time laws details

Question about the 30 hour rule with businesses trying to avoid full-time regulations. How exactly does the 30 hour rule Work ?

Is it 30 average hours per year per month?

Does it matter if you go over 30 a couple of weeks randomly ? Ex 36 34 32 20 20 15 34- since this skill well average under 30 hours ?

I'm asking this because I want to work the most hours at my job but we are not allowed to go full time over 30 .

I basically want to know is it fine to go over 30 a bit knowing that some other weeks I will be on vacation which will bring my average way down

Thanks