This may be a bit late to the party, but as someone who does bonsai IRL, I have some notes for a sequel or if this game is still being updated (this may get technical).

- Tree stem seems to be a bit random. It would be great if forms were implemented and selectable in the game (Bunjin, Chokkan, Kengai etc.)
- Wiring forms a big part of bonsai, perhaps having a system with branch tensions (branches can snap if too much pressure if applied) which would allow more agency for styling
- Tree taper can be influenced by the amount of branches near the top of the tree, thus perhaps such a system where energy should be balanced to improve health and design
- Adding to this, trunk correction would be great (this relates to selecting tree form) as this determines your style
- A mechanic where deadwood, shari or jin can be created would be cool, as adding tension to a tree and balancing this with harmony creates interesting designs
- An apical dominance system would be beneficial (when branches are allowed to grow at the apex of a tree they produce auxin and growth hormone that suppress buds further down)
- Directional pruning would be great as branches seems to continue to grow where you cut them straight, where buds will grow in a direction depending on which of them is closest to the tip (sideways up or down)
- To be able to add Nebari would be nice (the visual flow of roots at the base of the tree), as this draws your eye into the trunk and creates the sense of a sturdy tree
- Tree species doesn't really make sense currently as the tree with needles (suggesting pine) has the flowers of fruit trees (Prunus)

Overall, it has potential. Pretty nice, but I would rate it mixed.