20
aliens
× 2 |
2
engineering
|
22
modern-age
× 2 |
16
science-based
× 4 |
4
alternate-history
× 2 |
3
environment
|
5
mythical-creatures
|
5
shapeshifters
|
5
alternate-reality
|
10
espionage
× 2 |
0
natural-resources
|
4
slavery
|
1
antimatter
|
2
governance
|
0
nuclear-weapons
|
2
society
|
1
architecture
|
1
government
|
6
outdated-science
|
3
space
× 3 |
3
atmosphere
|
3
habitability
|
3
planets
|
6
space-colonization
× 2 |
6
biology
|
6
humans
× 3 |
26
post-apocalypse
|
2
spaceships
× 2 |
2
chemistry
|
0
interstellar-travel
|
16
psychology
|
2
space-travel
|
1
communication
|
13
magic
× 4 |
26
radiation
|
0
super-powers
|
5
dinosaurs
|
7
medicine
|
14
reality-check
× 4 |
4
technological-development
|
2
direct-democracy
|
1
middle-ages
|
0
robots
|
49
technology
× 6 |
5
earth
|
2
military
|
3
safety
|
28
warfare
× 6 |
fectin
