Does anyone know how to do rotation of 30% in 6 parts?

Hi all, I am new here.

I 've been facing some problems in my school work, especially with rotation.

Now, I have got this big disk divided into 12 parts. I have got a code that switch it part by part. When I press left, it switches from part 1 to 12. When I press right, it switches from part 1 to 2.

However, my teacher is not satisfied, and wishes for me to do it this way…whenever I press left, the disk slowly rotates a little bit until it reaches part 12. When I press right, the disk slowly rotates a little bit until it reaches part 2. In short, its not just 1 simple action that immediately goes to the next part, its supposed to be 6 smaller actions.

This is my current code

on(keyPress “<Left>”)
{
this._rotation-=30;
}
on(keyPress “<Right>”)
{
this._rotation+=30;
}

Could anyone teach me for to modify it to do smaller actions, but still switch part by part?

Thanks!