I generated this sequence 2102012210101111222011212000200220212200120102112020222211102212100010011012, find next 4 digits and explain the reason.
Note that this is a ternary sequence. All digits are generated by few rules, no digit is random or arbitrary.
Hint:
The sequence generated is periodic and the period is equal to 80 digits, but 80 (as any number greater than 3) does not appear in the rules