Changing the value in the Seed field will generate the corresponding input to the Input field.
Pressing the Download button will download the inputs for seed values seed, seed+1, ..., seed+#cases-1 at once.

By running your program locally against the generated input and pasting the output of your program into the Output field, the visualization results will be displayed.
Pressing the ▶ button starts animation.
By pressing the Save as PNG button, you can download the visualization results.

You can quickly switch between multiple outputs by pressing the Select File button at the top and selecting the directory containing the output files.
By naming the output file 1234.txt or abcd_1234.txt, the seed number (in this case 1234) is automatically set when the file is selected.

The left side of the visualization result shows the state of the board, and the right side shows the current snake color sequence and the preferred color sequence.
The color sequences are displayed in multiple rows as pairs of snake color (top) and preferred color (bottom), ordered from head to tail, from top to bottom, and from left to right in each row.
Hovering the mouse cursor over each cell will display detailed information in a tooltip.
Checking "show number" will display the color numbers in digits.
By checking "manual mode", you can move the snake with the arrow keys on your keyboard. You can also undo one move with the Backspace key.