Oh, that's strange! I'm sorry that you weren't able to play it :(
I'm not surprised though, as a French using QWERTY, AZERTY (and these days, German QWERTY) I probably messed up the control scheme... It seems to work on my side, do you press (assuming that you are on qwerty) Q + W (at the same time but Q first), then Enter? I can't debug it more than that as my workstation is... at work. So sorry!
Regarding the highlight the shader highlights the entire tile (including the "bottom" part).