In my Felltower game, we've been mucking with explosive spells a lot.
This is to replace the really anemic explosive spells as they are written now:
"The target and anyone closer to the target than one yard takes full damage. Those further away divide damage by three times their distance in yards (round down)." (GURPS Magic, p. 75)
That works out to full damage in the center hex, 1/3 to the surrounding ring, 1/6 around that, 1/9 around that, 1/12 out to four, etc. So you get a damage-variable size, with pretty low damage results out past the center and the ring around it. Even an 18d Explosive Fireball doing max damage (108 points) does 36 damage, then 18, then 12, etc. Average damage is noticeably smaller, but still does 63, 21, 10.5, 7, etc. (and costs 36 base energy, so it should be good.)
A more reasonable 6d Explosive Fireball does 21, 7, 3.5, 2.33~, 1.75, etc.
I prefer a less variable area of effect, given that pretty much all GURPS spells are precisely sized. You don't throw a spell and then find out how big the effect was.
I also like fireballs that aren't a lot of expensive for potentially high damage to an impact/point blank target plus a high chance of almost no damage to moderately armored folks 1-2 yards away.
What we've been doing up to now has been -1d of damage per yard away. Potentially really big - an 18d spell is 35 yards across!
Another simple way to have decreasing damage but standard effects is this:
- All explosive spells expand to 1 yard (if 1d), 2 yards (2d), or 3 yards (3d+). (Preserves the variable size from 3e)
- Explosive spells do full damage in the center hex, 2/3 damage out to the surrounding hexes, 1/3 damage out to the hexes around that. (Preserves 3e size, keeps a single roll)
Still another would be to say:
- All explosive spells are 3 yards across.
- Divide damage as above (round down, min 1).
That makes all explosive spells a 3-area spell (1 hex, the 2 rings of hexes around it). Damage is one roll, and easier to calculate.
You could make these things even more effective, if you had no reduction in damage within their size. 6d? Does 6d to everyone in the area of the spell. That's pretty scary, and easy, but it cuts down the downside of 4e explosions (variable area) and reduces the utility of area attack spells (uniform damage over an area).
I kind of like the middle option. Single size (no tiny explosive fireballs), easy damage calcs. If Hannibal the Flammable throws a 5d explosive fireball and rolls 17 damage, he'll do 17, 11, 5 in the three rings of hexes. The max-damage 18d example above would do 108, 72, 36. Done. Average damage would be 63, 42, 21. Well worth the cost for the annihilation that probably brings (damage plus everything bursting into flame at that damage).
Easy enough. Quick thirds instead of 1/3, 1/6, 1/9, etc. No variable area that depends on rolls to see how big it is, which slows down combat a lot for little gain once foes have DR 3+.
Will we do this? I have no idea. But I am thinking about it. It wouldn't change any recent events, and it would make those 1d Explosive Fireballs Hannibal loves so much more potentially useful - now they'll hit a 15' diameter circle for at least a little damage) instead of nothing but the target. He might get lucky and do 2 damage to his target's neighbor's neighbors.