I am glad you like my game! I am also not very happy with the forest tiles. Unfortunately there are no real wall-like forest tiles in the tileset. And there are also no concave corner tiles. So I only use the fully-filled-forest-tiles together with some treetop-tiles at the borders. But the overlap is too big which makes it a little messy. I will have to rework it one day.
But fortunately there is an easy workaround for this. Simply switch to the ASCII-mode on every forest level. You can do this by pressing [g] on your keyboard. Pressing [g] another time brings you back to graphical mode.
I am currently implementing a server-side backend. Once this is done there will be automatically updated scoreboards and a lot of statistics. An achievement system is also thinkable. But of course this is a lot of work to do. Therefore it will take a while until I have time to care about the forest-tile-problem.
I hope you will have some fun anyway! :-)