Hardmode Progression is a simple mod that is designed to introduce extra challenge to the general gameplay loop of Minecraft without causing excess tedium or annoyance.

While Netherite equipment is unmodified, all other vanilla gear has been nerfed slightly to accommodate the introduction of three new tiers of materials; Copper, Cupronium, and Anoxite.

Additionally, certain tiers of tools are now required to successfully harvest and quickly mine certain types of blocks. All deepslate-tier blocks require at least cupronium tier to harvest, and all nether-tier blocks require diamond tier to harvest.

A brief summary of where the new tiers fit in the hierarchy:

Wood => Stone => Copper => Iron => Cupronium => Diamond => Anoxite => Netherite

or, for Armor, Leather => Copper => Iron/Chainmail.. etc

A core design tenet of the mod is the hierarchy of utility between materials.

Wood and stone are unchanged in tech progression.
Copper Tools can now be crafted, which require copper ingots.
Copper Tools allows the harvest of Iron.
Iron Tools allows the harvest of Nickel, a new type of ore. It can be used to create Cupronium, which is a combination of Copper, Iron, and Nickel ingots.
Cupronium Tools allows the harvest of Diamond, which can be combined with Cupronium ingots to create Diamond Ingots, which is now used to create Diamond Tools.
Diamond Tools allow the harvest of nether-tier materials, which can be used to create Anoxite Ingots.
Anoxite Tools allow the harvest of ancient debris, which can be combined with Anoxite Tools to create Netherite Tools.
This means that, except for Stone, all tiers of tools rely on previous material tiers. This encourages players to continue collecting resources that might otherwise have become irrelevant later on.