i have a suggestion for the clipboard, block copy, paste and rotation, and maybe a description on what the clipboard does, it is kind of confusing ,
a upgrade to the drag fill system would improve building, such as diagonal wall / sloped floors, a outline for single block placement would be useful for building with floating offset blocks
a button that toggle air/block mask fill could be useful, or a crouch multiselect that allows you to select separate areas for filling
a ladder or climbing surface tool would be interesting, maybe for the zombies to use for climbing fences and stuff, select areas could have them
a navigation tool for advanced nav creation, for zombies to climb or make farther jumps along selected areas would be awesome, imagine taking the stairs to try to outrun zombies, only for them to leap across rubble to get to you,
certain blocks could use a connected texture variants, like glass and logs, log block could use a rotation property for fallen logs and stuff
the checkered block is kind of wonky to build with, it randomly flips direction, making checkerboards are impossible, maybe you could split the checkered texture between two versions, regular, and flipped, or you could make a texture flip tool for reversing texture direction
if you need or want any suggestions, i have plenty of ideas
ooh, wallpaper 2 could look like the backrooms wallpaper,