Its a simple block that looks like glass and when you power it, it changes its color to black when you dont change it.
You can change its texture when turned on with cable obscurator.
Or you can make advanced photochromic glass which will take texture from upper right block.
Now you can make windows without moving blocks or trapdoors!
Photochromic door is not that simple as glass, when you power it, it changes its texture and becomes solid(you cant go through it).
And when you unpower it, it becomes invisible and you can go through it.
You can change its texture in powered mode by using cable obscurator. You change it same way as cables.
When you leave it without setting it, it will take texture from upper right block. When you power it with medium voltage it
will shock you, when you try to touch it when turned on. When you power it with high voltage, it will explode.
There are also reinforced ones, just use reinforced glass/stone/door.
Also when powered, these blocks have durability of copied block.
And if you would right-click on this with a bucket of water it will change its graphical state.
So if an photochromic door is closed and you will right-click it with water it will look like its open but you wont be able to go through.
Crafting recipes:
Photochromic glass:
[G][G][G]
[G][C][G]
[G][G][G]
Advanced photochromic glass:
[G][G][G]
[G][AC][G]
[G][G][G]
Photochromic door:
[D]
[G][AC][G]
[D]
G = Glass
C = Circuit
AC = Advanced Circuit
S = Stone
D = Door(Iron)