I'm a casual player, so take these with a grain of salt. After playing around for less than ten minutes, I stumbled upon the following issues:

1. The outer boundary of the scene should be targetable for placing blocks.
2. Pressing the CTRL key should make the mouse movement slower, for easier precise placement of blocks. Though I suspect there might be a more popular choice for such a key in other software related to 3D-modeling.
3. The `?` (Shift+`/` on the American layout) is a popular shortcut for showing the keyboard shortcuts help, especially on websites. For example, it's used by YouTube, Twitter, GitHub, Atlassian software (Jira, Bitbucket, Confluence), and Reddit Enhancement Suite. I kept muscle-memorying `?` even after learning that Luminal Spaces uses `H`.

Thanks so much for your input!

1. As is said in the project description, the scene size is currently fixed at 32x32x32 voxels for technical reasons. Placing blocks on the outer boundary would exceed this limit. You could argue that the outer boundary shouldn’t be selectable in this case, but I’m planning to remove this restriction in the future, so I didn’t bother handling this case right now.

2. CTRL is already bound for slowing down camera movement. I tested several variants of using the same keys to also slow down the mouse, and in my opinion just moving closer to the target blocks is the simplest solution.

3. I’ve added the ‘?’ key as an alternative to show help, this should work in the next release.