Tree Shading
Unfortunately, I'm not really sure how to explain this in a simple way, but I'll do my best to make a clear set of rules.
Let's call these tiles the
roots
Then these can be the
middles
This tile is the
top
And these can be the
transitions
Note that the one on the left is the shaded version, and the one on the right is the unshaded one.
So, here's the step by step process.
1. Lay out the shape of the trees you want to place using the shaded versions of these tiles
2. For the bottom set of transitions, replace them with shaded roots.
3. Add tops to the trees.
4. All the tiles that are not adjacent to other tree tiles should no be replaced with the unshaded versions. I've circled the ones I changed to be extra clear.
5. Last step. Any middle that is directly below a top (circled in red) or adjacent to another middle directly below a top (circled in blue) should be replaced with the unshaded version. A little unclear, so once again I've circled the affected tiles.