itch.io

Or, you can use something like this:

{
"base": {
    "attribute_name": "sta",
    "attribute_type": "current",
    "adjustor": "*",
    "adjustment": "1",
    "lowest_req" : "0",
    "highest_req" : "65535"
},
"compare": {
    "attribute_name": "health",
    "attribute_type": "current",
    "adjustor": "*",
    "adjustment": "0.01"
}
}

This method will create cost in "sta" fully depend on current health.  More "health" more cost of skill. Zero "health", zero cost of skill, (in this part of fully cost).

And use zero change in base part of cost, you can do it many times in one skill, and make cost in "sta" depending from many other stats.