Unlike most other games of mine, Cosmoclasm isn't set in the past but in a science fiction future. Nevertheless, the theme is timeless as it deals about conflict and area control. One idea was actually to set the game in the Swedish Era of Great Power, where the players would take on the roles of nobles spending arms and building castles to control the newly acquired provinces of Sweden. On the other hand my first six games were set in this historical period so a space theme felt refreshing for a change (and, to be honest, most people don't share my interest in Swedish 17th century history).
So how well does the science fiction theme explain what happens in the game? Fairly well, but it's clear that Cosmoclasm is a mechanisms first - theme later kind of game. Let's start with the cards.
The force cards have five different symbols that all make sense to a planet conquest. Drones, fighters, mechs and missiles are all modern weapons that could be part of a science fiction story and it makes sense that you need superiority in a weapon type to claim supremacy. It also makes sense that stargates allow you to quickly move to the next planet and in that way decide where the next battle will stand. But how can you win a battle by specializing in one weapon type only? Perhaps it would have made more sense to reward different weapon types but that wouldn't work mechanically.
How about the different suits of the force cards then? One could argue that different planets require differently adapted weapon types, e.g. mechs suited for a cold and dry planet wouldn't work on a hot and wet planet. But if so, how do you explain why one player can attack with mechs for cold planets and another player with mechs for hot planets? It would have made more sense to allow only one suit for all players but that would give the first player a too strong advantage. Hence, I decided to choose the more generic suits of sun, moon, star and eclipe (non-planets with clearly distinctive colors).
OK, let's forget about the cards and move on to the planets. The planets are all authentic (the 8 planets of our own solar systems plus Pluto and the largest moons Eric, Callisto and Ganymede). It also makes sense that most battle stations around a planet help controlling it. But how can a battle station control several planets? While a border castle can control all bordering provinces, the distances between planets are too vast to allow such control. No, not even the battle stations make much sense thematically.
Finally we have the factions, a word I preferred to the common but sensitive word "race". The Humans have an obvious place, as do their fictional but frequent adversaries the Martians. The ability to specialize made sense thematically for the Humans and was abstractized into the ability to switch one force during the card play. Likewise, since the Martians always get beaten and always come back, the ability to regenerate and regroup made sense for them. this was abstractized through their ability to move around battle stations.
The Hiveminds, bugs directed by some kind of central mind, appear in many science fiction stories. Since bugs are found everywhere, they were given the ability to adapt and ignore the suit, i.e. the conditions necessary to use a particular force. The Cyborgs are even more common and since machines can produce machines, why not give them the ability to draw an extra card to reflect their production capacity?
The Radiants are fairly original. The idea come from an old discussion which source I don't remember but where it was suggested that alien life forms could be something completely different from what we are used to, such as "intelligent energy". Perhaps the beings in 2001 - A Space Odyssey are something like this? Since they don't seem to bother about distances, they received the Stargate bonus, giving them an advantage when it comes to select the next planet for the round.
In conclusion, the theme may contribute to convey an epic science fiction feeling but other themes could just as well have supported the game mechanisms.