More directional blocks.

I propose assigning a specific orientation to each block—similar to how logs work. This would allow for vertical planks instead of just horizontal ones.

It would also be possible to make existing slabs and stairs placeable vertically.

For instance, alongside the standard block placement grid, an advanced grid consisting of five zones could be added: a small central square and four trapezoids along the sides.

Clicking the central square would place the block aligned with the grid's current orientation.

Clicking one of the four trapezoids, however, would place the slab or stair facing a different direction.

You could switch between these modes by pressing the Alt key.

In other words, there would be no need to add new "vertical" block types; the game's placement system would simply need to be modified.