Here's a quick overview of the controls:
Click on a piece to activate it and see available moves. Click again to move. Pieces that have already moved show a "lock" icon:

When an artillery is activated, you may rotate it by moving your mouse around the dotted circle. Click to set rotation. Don't forget that you get a free rotation after you move:

Infantry will automatically engage with each other when possible:

If an infantry can capture one or more infantry units, crosshairs will appear. Click on one to execute the capture:

Mousing over the End Turn button displays crosshairs on all friendly units that will be captured at the start of your opponent's turn:
