Here's the new mechanics:
* Previously, the first health upgrade cost you 16 and then it would go up by a power of 2 from there for each further upgrade (32, 64, 128, etc). Mana and Attack were the same, except starting at 8 (so then 16, 32, 64, 128, etc).
** Now the fee is flat for all upgrades: it's 20 stones for a health upgrade, and 10 for attack or mana.
** After much discussion on this subject, it became clear that being able to apply 10 upgrades to your character is an important avenue for player choice, but not something that should be prohibitively time consuming to do. Even if the upgrades past the 8th were a "bad value" to encourage players to consider conserving stones, some players would push all the way to 10 upgrades no matter what and then be encouraged to save-scum to protect that character.
** Further, not having 10 upgrades on the primary character was creating a disincentive to create a stable of other characters for various purposes.
** Lastly, it was tricky to balance the game because if players used a full 10 upgrades then things could be far to easy; but with no upgrades it could be far too hard. Now we can balance around the general expectation of roughly 10 upgrades being on most characters; and these upgrades being more about choice than they are about a long-term slog through getting thousands of stones.
** The reason for keeping a cost to the upgrades at all is to maintain that sense of loss on death of characters; aside from the vengeful ghosts, upgrades are the one thing that is lost when your character dies. That has seemed a very popular thing (and in fact upgrades were originally added when beta players felt there was not enough of a penalty for death), but we have been aiming to balance it so that the penalty is noticeable but not harsh.
* Previously, each upgrade that you applied in the health, mana, or attack categories would give you a flat bonus every time you used an upgrade. That made sense when the costs of each upgrade went up exponentially. However, now that the costs are flat (not even linear, but literally flat), we chose to instead make the bonuses from each upgrade decay so that they remain balanced.
** Applying 10 health upgrades now gives a maximum 5.57x bonus (so 20% decay) compared to 10x previously (0% decay).
*** With a character of base health 141, that gives the following progression: 141,282,395,485,557,615,661,698,728,752,771,786
** Applying 10 attack upgrades now gives a maximum 1.65x bonus (so 10% decay) compared to 2x previously (0% decay).
*** With a character of base attack 85, that gives the following progression: 85,93,100,107,113,118,123,127,131,135,138,141
** Applying 10 mana upgrades now gives a maximum 2.63x (so 30% decay) compared to 6x previously (0% decay).
*** With a character of base mana 100, that gives the following progression: 100,150,185,210,227,239,247,253,257,260,262,263
** Cumulatively, these changes do help to encourage players to choose characters with base stats that somewhat mirror what they want the final stats to be -- because the changes you can make to a given character are somewhat less extreme, although still really notable. The penalty for diversification is also a lot less now compared to what it was, but the penalty for stacking everything into one stat is now a penalty of effectiveness rather than of cost.
* Mana upgrades have been the least useful of the three kinds of stat upgrades for a while. Part of that is because most of the really high-mana-cost spells that we have planned are not yet in the game. So some of that is just a matter of intent for later stuff.
** However, to address this imbalance in general, we made it so that mana upgrades also simultaneously upgrade mana regen rates. Normally all characters have a flat 83.3 regen rate for mana unless they have had some mana upgrades via upgrade stones; given that upgrade stones are the only way to increase mana regen, that makes this suddenly a lot more interesting.
** Applying 10 mana upgrades now gives a maximum 1.3x bonus to mana regen (so 10% decay on 1 5% boost per increase) compared to 0x previously.
*** So the progression for any character is: 83.3,87.3,91.3,94.3,97.3,100.3,103.3,105.3,107.3,109.3,110.3,112.3.
* The logic for how you find upgrade stones has been changed up somewhat:
** Places that previously dropped 8 upgrade stones now drop 5. Places that dropped 16 now drop 10.
*** Except in the intro mission, where the caches of 8 are now caches of 50, and the caches of 16 are now caches of 100. This lets players explore these mechanics a lot more right in the intro mission.
** Places that previously dropped 4 upgrade stones now drop 5, and those that previously dropped 3 now drop 1.
** Now when you kill a miniboss, you get 5 upgrade stones. When you kill a microboss you get 1.