I was in my study thinking about hit dice. In a "disassociative fugue state,*" I put the words "hit dice" and "to hit" together. I imagined an alternate combat system where hit dice stood for a character's attack value rather than it's defense value.
I wrote a bunch of little notes on my phone's note pad, and emailed them to myself. They don't make a lot of sense but maybe you can do something with them? Probably a lot more than this little girl and humongous fish guy.
To attack: roll all hit dice. Every 5 or 6 is a hit.
Attacks carry over from one target to the next (eg a two hit result against two 1HD enemies kills both).
Armor grants 1, 2, or 3 saving throws. A successful save negates a hit. Saves are successful on a 5 or 6. A shield only provides a save against missile fire.
Characters have 1 hit point per die. Pluses (any number) count as 1 extra hit point, indicating they're tougher to kill. Starting at level 4, PCs must be killed by simultaneous hits equal to their total hits (eg 4 hits for 4 HD, 5 hits for 4+1, etc.), making them nearly impossible to kill by normal types.
On attacks, the +1 etc. on the Hit Die adds that many to the hit range of 5-6 to one of the Hit Dice thrown, therefore increasing the chance of a hit with that single die.
So there. That's what I wrote in my "disassociative fugue state."
*spacing out, man