These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.99 s (backtrack: 0/20).

[ebuild  N     ] sci-biology/tree-puzzle-5.2-r1::gentoo  USE="-mpi" 855 KiB

Total: 1 package (1 new), Size of downloads: 855 KiB