Find the solution to this slitherlink puzzle that I came up with:
This one's even smaller!
This solves it uniquely. I've only outlined the steps but can give more detailed explanation if needed.
Started with 3s in corners (drew 2 edges for each).
Using the 2s I worked out the centre square is either bottom or left-top-right. So 2 up-right from it has top-right edges both on or both off, so the 3 on right has bottom and right on.
The bottom 1 I tried and eliminated (took a while) three edges so the top one is on. Eliminates other edges of the 1 above, makes the center square left-top-right.
The bottom loose edges of 3s have to turn upwards, lose ends of the edge between 1s have to go straight on. Remaining loose ends of 3s go up (straight on), the 2s in 4th row can only have the second edge on top.
That determines which 2 edges are on for each of the three 2s on top area.
Continue the loose edge of the 3 near the top right of the grid: up, left, left. Connect both loose edges from right, just follow left and then down.