Body Temperature: goes up or down depending what biome or dimension your in. Drinking water bottles makes body temp go down. If your body temperature is 3000 or -3000 you die leather chestplates increase your temperature

Exhaustion: If you don't sleep in a bed after 11 Minecraft days you die

Thirst: When you jump your thirst goes down by 100, just standing still makes your thirst go down by 20 per second, your thirst goes down faster in the nether. To get hydrated drink a water bottle or eat melon or crouch in water

Nutrition: When you eat something unhealthy it goes down by 1 if you eat something healthy it goes up by 1 unless its a golden apple or a enchanted golden apple. When you get to -6 you die

Broken Legs: When you fall 10 blocks you break your legs which means you will not be able to move or jump unless you have crutches on your offhand and mainhand. After 720 thousand ticks your broken leg will completely heal

Armor Weight: this feature applies to netherite armor, golden armor and diamond armor when wearing one of these armors your speed gets subtracted by 0.01.(this feature gets laggy)

You can only die 1 time

your inventory is gone you can get more space by making a backpack by throwing 1 iron bar and 8 of any type of wool of the same color on the ground(make sure you throw the iron bar on the ground first)

Crutch: used to allow people with broken legs to walk. To use it have a broken leg than put one in your mainhand and offhand. To make it you need 4 black wool and 3 iron ingots.

This is my first data pack so if its bad to your standards than that's why.
Make sure you do /reload when you get in the world with the datapack.