Put a square, circle, or triangle in every white square. When 3 adjacent white squares are in a line horizontally, vertically, or diagonally, they should contain exactly 2 of one of the symbols. In other words, 3 consecutive symbols cannot be all the same or all different.

1. | 2. | 3. | 4. | 5. | 6. |

7. | 8. | 9. | 10. | 11. |

12. | 13. | 14. | 15. |

16. | 17. | 18. | 19. |

The solutions are here.