1.
| 2.
| 3.
| 4.
| 5.
| 6.
|
7.
| 8.
| 9.
| 10.
| 11.
|
12.
| 13.
| 14.
| 15.
|
16.
| 17.
| 18.
| 19.
|
The solutions are here.
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.