Short answers. Honest meters.

Because the costs are per-minute: server compute ticks while the shard is live, load follows actual bytes moved, and the host's hourly rental prorates per minute. Per-minute metering means a 10-minute drop-in costs a sixth of an hour-long siege — and a stopped shard bills nothing further.

100 coins is exactly $1.00 (1 coin = $0.01, 1 coin = 100 centicentcoins). Every figure already includes the 25% platform cut — never added on top. Money math runs in integer centicentcoins, so split shares land dust-free.

Insufficient coins for this session. The billing check compares your quoted share against your live ledger balance (SUM over coin_ledger, read-only) before anything moves — short balance answers 402 and nothing is billed. Top up, confirm the shown total again, and retry.

Band-blocked, not broke. Your band may not enter that shard's band (kids→kids-only, teens→kids+teens, adults→all), or the room sits below its game's minimum band. The reason names both bands. Coins are untouched — fix the room choice, not the wallet.

Quote mismatch: the accepted total must equal the quoted player total exactly. Prices move as players join and leave, so re-read the fresh quote and confirm that figure. Malformed input and unknown servers also answer 400 — never a charge.

Fail-closed, same as players: the short side answers 402 and nothing bills — nobody is half-charged and no phantom session is written. Until the guarded ledger settlement lands, both rent and billing return quotes only (charged: false), so past quotes are never back-billed.

Kids rooms (0 coins per player per minute) and any room whose host flips hostFree — the host pays server + load + rental, players pay 0. Your receipt is /my/usage/; your balance is always SUM(delta) over your ledger rows.

Never. Birth dates are checked in memory on your own device for that check only — never sent, never stored, never remembered. The shard gate itself compares bands only and stores nothing either.