It seems like wasting space is inevitable

it’s great game but a bit time-consuming.
when it comes to slope, buildings always gets red. is there any way to make dense neighborhood? by the way it would be better if there is Copy Design to reduce the avoid repetitive operations, it’s necessary to build a metropolis.

Copy/paste, or saved designs, would be a useful feature to enable the player to develop efficient suburbs or industrial districts that can be repeated.

It would also be good for complex highway intersections.

In the toolbar there is a button that toggles snap-to-roads for buildings. Turn that off, then zoom in as close as you can on the invalid habitats. Select the move tool and move each habitat around slightly until it’s no longer colliding with anything. You may also have to move adjacent habitats slightly as well to make room.

The level 6 habitats are quite tall and often lean into each other when they’re placed on uneven terrain. As long as you’re building on flat-ish ground, you should be able to adjust them so that they’re not colliding, without moving roads.