Design a consistent hard-magic system with costs and limits

You are a senior worldbuilding consultant who designs hard magic systems — rules-based, internally consistent, and dramatically useful — in the lineage of Brandon Sanderson's laws.

Design a hard magic system for my setting. The goal is a system where the limits create the drama, not the powers.

Setting & intent:
- Genre & tone: [FANTASY / SCI-FI-FANTASY / DARK — AND THE FEEL]
- Tech level & setting: [MEDIEVAL / INDUSTRIAL / SPACE-AGE]
- What magic should DO in the story: [THE PROBLEMS IT SHOULD SOLVE — AND THE ONES IT MUST NOT]
- Energy/cost source you imagine: [e.g. 'LIFE FORCE', 'RARE MINERAL', 'MENTAL FATIGUE', 'NOT SURE — PROPOSE ONE']
- Desired hardness: [HARD (fully explained) / MEDIUM (rules implied)]

Design the system with:
1. The core rule — one clear, memorable principle the whole system follows. State it in one sentence a reader could repeat.
2. What is possible — the categories of effects the system enables, with concrete examples. Keep the surface area small enough that a reader can hold it.
3. Costs & limits (the heart of a hard system):
   a. The personal cost — what using it takes from the practitioner (energy, lifespan, sanity, material).
   b. The hard ceiling — what is flatly impossible, and why. This protects plot tension.
   c. The trade-offs — using more power costs more; no free scaling. Define the cost curve.
4. Failure modes — what happens when a spell fails, is overused, or is botched. Magic should be able to go wrong, not just cost a fee.
5. Consistency checks — two proofs: name a plot problem this magic would trivially solve (and how you constrain it) and one it cannot solve (and why that is good for tension).
6. Skill & learning curve — who can use it, how long mastery takes, and what separates a novice from a master. This drives character arcs.
7. Economic ripple — three concrete ways this magic changes daily life, labor, or trade, so the world feels lived-in.

Rules:
- Internal consistency is non-negotiable. If two rules could contradict, resolve it.
- Every power must have a cost the character feels. No free magic.
- Resist power creep. If an effect would break the plot, it must be impossible or ruinously costly.
- Do not overwrite the mystery. A hard system can still have unknown edges; say where the known rules end.

Output: the core rule, powers, costs/limits/ceiling, failure modes, consistency proofs, skill curve, economic ripple.

Success signal: the output is good only if there is one clear core rule, every power has a felt cost, there is an explicit hard ceiling protecting tension, and you provided a consistency proof showing a problem the magic cannot trivially solve.