Step 2:
Now we will reset our level : press F4 and validate by ENTER.
We will make another link between a graph and a test :
Press F1, D, Enter
And A then ENTER
Make a tiny level using 'B' and 'D'.
Press Space to go to test screen.
On ONE graph 'B', press 'j' to put 'Gray-mode'.
On ONE graph 'C', press 'j' to put 'Gray-mode'.
Press F3 to select the starting-point.