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 value of V is displayed at the top left of each cell, and the value of L is displayed at the top right.
At the bottom of each cell, the player number who selected that cell as the move destination is displayed.
The color of each cell represents the owning player, and the higher the value selected in color mode (V or V×L), the darker it is displayed.
By checking Manual mode, you can manually add operations by clicking on each cell.
Also, by pressing the Backspace key, you can undo the last move.
When Manual mode is on, the cells that player 0 can move to are highlighted with a red border.