Lock a gold token and get back one NFT. Its picture is a heap of coins, and the number on the heap is exactly what burning it returns.
The wallet
Every pile below is drawn at the same scale, so you can see the sizes against each other. Up to 40 there is one coin for each unit. Above that the heap gets bigger and prints the exact amount.
Same scale: one coin is the same size in every tile.
Examine
The picture comes only from the amount. The same balance always draws the same pile. When one unit is added, one new coin lands and the others stay where they were.
Twelve units, twelve coins. Count them.
Past forty, the number does the counting. It never rounds.
Move gold around
Two piles become one, or one pile becomes two. The totals always match.
Give it two piles. Get back one pile holding the sum.
Give it one pile and an amount. Get back two piles that add up to the original.
The promise
Burn a pile and you get the gold token back, exactly the number printed on it.
The picture is drawn from one integer: the base units locked inside. No rounding, ever.
If there is ever a fee, it comes off before the number is written. The number on the pile is yours.
The locked balance does not shrink over time. A pile of 40 stays a pile of 40.