So, I've played Supernova 3 times now. Most of the players I've played it with have found it a clever game, but somehow close, but not quite; most of us agreed a couple minor house rules would be necessary to get it on the table again. I've felt since the first pay that it needs a couple tweaks to put it over the top, but now I have some suggestions.
There are I think 5 key problems:
1. The draw of the battle cards can be incredibly swingy because of the huge variance in card strengths and the difficulty in cycling cards
2. The High-impact battle cards have a bunch of confusing rules associated with them, but often seem to be weak to useless to actually harmful, but hard to get out of your hand
3. Comms seem under-powered
4. Intermediate scoring seems very coarse, while end-game scoring is almost too fine.
5. Even the "short" version runs a bit too long.
Fortunately, I think these are potentially easy to tweak.
1) and 2) It pains me to suggest it, but I think the High Impact Battle Cards should just be removed from the game. The Power Inverter is a terrible card, always worse than just drawing a 3, plus it can actually hurt you. Dual Seeker is always worse than just drawing a 4 or a 5. Only the Smart Bomb seems definitively OK, but again almost all the time you'd be better off just drawing a 4, and you'd always rather have a 5. The additional playing restrictions on these cards also make them constraining. If they were powerful but hard to play that would be one thing - but they seem just average battle cards that are hard to play and introduce a bunch of awkward rules grit. If we wanted to keep one, we could just keep the Smart Bomb and ditch the other two.
1) Instead of fiddling your hand in step 5 if no battles occured, just let a player discard as many battle cards as he or she would like and draw replacements. Then in the purchasing phase, for 1 RU you can draw three, keep two, and discard one - allowing the player to hold extra cards over their comm limit. Or something along these lines to make this purchase a little more worthwhile.
1) and 3) Allow the players to replenish to the Comm level in 1) and then in 3c) of their (not opponent's) turns. You still just replenish to 4 on other players' turns.
On the flipside of this, if you play an invalid hand, you have to form the strongest valid set from the cards played and take the rest back into your hand instead of discarding them. In my games, invalid hands became a key way to get rid of useless HI battle cards.
4) For end-of-phase scoring (phases 1 and 2), you get a half-point for each occupied hex on the board. It's not a lot, but it would make intermediate scoring slightly more interesting. At the end of the game, you don't get points for RUs. As it is currently, players are always trying to figure out whether spending an RU will bring them a point or not; it's not terrible but not great either and it slows the game down. This way you just have to worry about saving for the final flare instead of balancing every expenditure.
5) We solve this by tightening the screws on the rest of the game so that the length isn't as much of a problem