This is the page for describing the ways Kid Mystic calculates certain internal numbers. The baseline to understand is that all non-whole numbers are rounded down before they are used in the game. This means even if the number to be used is 37.99, it is rounded down to 37.00.
The flooring occurs after every calculation, this means that the order in which multiplication is done makes a difference. Unfortunately, the correct order is not known. Take care in your calculations to try a few different combinations to see if you get different results.
Defense[]
Unlike in LL2, only the player character has defense. There are two types of defense in Kid Mystic. The first is obtained from buying hats in the Shop. This defense is a simple number which affects damage done in the following way:
DMG1 = ATK - DEF
ATK is the base damage the monster (or lava) can do.
DEF is the defense value of the hat you're wearing (see Shop).
DMG1 is the total amount of damage taken from your health if there are no other modifiers (see below).
Armor[]
The second type is obtained from the Fairies Blocky Fairy and Toughy Fairy, and from the spells Stoneskin and Steelskin. It is also obtained from Shield Stones in Madcap Mode. This defense is referred to as armor. There is also one fairy (Runny Fairy) that increases damage taken. In the calculations, all armor is accounted for after the above defense:
DMG2 = floor( DMG1* (1-(SH/100)) * (BF) * (TF) * (RF) * (SS) )
DMG1 is the same as in the calculation above.
SH is the amount of Shield Stones, up to a maximum of 99. This essentially means each stone takes 1 percentage point away from the total damage, to a minimum of 1% damage.
BF is 0.75 if Blocky Fairy is equipped, 1 if it is not.
TF is 0.5 if Toughy Fairy is equipped, 1 if it is not.
RF is 1.25 if Runny Fairy is equipped, 1 if it is not.
SS is 0.5 if Stoneskin is active, 0.125 if Steelskin is active, 1 if neither is active.
floor means all damage is rounded down to become a whole number. This means both 24.16 and 24.89 get rounded down to 24, even though they're different. Note that each calculation result is floored before multiplying again. The order in which this happens is unknown.
DMG2 is the total damage taken from your health. Note that this cannot go below 1 unless the spell Stoneskin/Steelskin is active. In this case, damage done can be completely nullified if DMG2 is less than 1, even if it's 0.99.
The complete calculation is as follows:
TotalDamage = floor( (ATK-DEF) * (1-(SH/100)) * (BF) * (TF) * (RF) * (SS) )
The maximum amount of damage to still be nullified is 1,607. With the Steel Hat, 99 Shield Stones, the Toughy Fairy equipped, and Steelskin active, this gets lowered to 0.999375, then floored to 0. 1,608 is impossible to nullify, being decreased to 1 with the above. Note that both of these are impossible to encounter in Madcap Mode, as every damage amount ends in a 0 (due to everything being multiplied by 10). So 1,600 and 1,610 are the theoretical "true" values.
Experience[]
All monsters give experience on death until you reach level 50, at which point the experience is converted into coins at a rate of 1 coin for every 5 XP. For example, the Spitter gives 50 XP. After level 50, this changes to 10 coins. Note that the extra coins aren't actually dropped on the ground, they are instantly added to your coin total. This means killing aquatic creatures can still be worth it after level 50. Also, XP multipliers below apply to coins given in the obvious way.
Fairies and the Light of Wisdom can have an effect on your experience.
TotalXP = XP * (WISDOM) * (GRABBY) * (SMARTY) * (MADCAP)
XP is the base XP given by the monster.
WISDOM is 1.5 if the Light of Wisdom is purchased, 1 if it is not.
GRABBY is 0.75 if Grabby Fairy is equipped, 1 if it is not.
SMARTY is 1.25 if Smarty Fairy is equipped, 1 if it is not.
MADCAP is 5 if Madcap Mode is active, 1 if it is not.
Each calculation is floored after each multiplication. This can cause a different result depending on the circumstances.
For example, the Mushie gives 25 XP on death. With the Light of Wisdom, this raises to 37. With the Grabby Fairy this drops to 18. With both this almost cancels out to 27. Note that this is not 28, which it would be if the calculation was simply:
TotalXP = floor( 25 * 1.5 * 0.75 * 1 )
AKA
28 = floor( 25 * 1.125 )
This is not the case. as mentioned above, the floor() function happens every time.