Or you could have a mode where you just tap it, and it "rolls a d20", where the RNG generates a number from 1 to 20, and then animates the faces rolling around

Or you could have a mode where you just tap it, and it "rolls a d20", where the RNG generates a number from 1 to 20, and then animates the faces rolling around a little and finally ending with the random number chosen on top.