The nine points

1. Note: here “thinking outside the box” is literal: the restriction of not leaving the square was not in the statement.
2. The visual key: Notice how the lines extend BEYOND the dotted square made up of the 9 dots. This extension is essential to be able to connect all the points with only 4 continuous straight lines.
3. 🟢 Line 2 (Green): Diagonal from above point 1, passing through points 2→6→9, extending to the right.

Answer: The solution requires extending the lines beyond the square formed by the points.
Why the conventional approach fails:
If you try to keep the lines within the imaginary 9-point square, you will need a minimum of 5 straight lines. With only 4 lines it is impossible... unless you leave the square.
Solution visualization:

Diagram interpretation:

• 🔵 Line 1 (Blue): Vertical that goes up the left column (points 7→4→1), extending upwards.
• 🟢 Line 2 (Green): Diagonal from above point 1, passing through points 2→6→9, extending to the right.
• 🟡 Line 3 (Yellow): From the right, return horizontally through points 9→8→7.
• 🔴 Line 4 (Red): Diagonal connecting points 3→5→7, extending beyond the square to the top-right.

The Visual Key: Notice how the lines extend BEYOND the dotted square made up of the 9 dots. This extension is essential to be able to connect all the points with only 4 continuous straight lines.
Key idea:

"Thinking outside the box" is not just a metaphor in this problem.> It's literally the solution: your lines MUST come out of the imaginary square
which form the 9 points.

Note: here “thinking outside the box” is literal: the restriction of not leaving the square was not in the statement.