Pretty nice game!
I like it a lot, I have some suggestions:
You could let the players choose if they want to leave an empty spot in beetwen actions, so there will have more strategy involved.
You could add an undo button because sometimes I missclicked or I wanted to make a change and it was kind of frustrating not being able to change my actions.
Also I think the game over screen don't work right, I couldn't press the buttons.