Ledger

a deficit is not money vanishing. it is an entry that must show up elsewhere.

tap transactions in and out and watch reserves take whatever the other two accounts do not

A country buying oil, exporting software, and taking a foreign loan are not separate stories -- they are entries in one ledger, and that ledger has to close at zero. The current account tracks trade and income crossing the border; the capital account tracks investment and loans. Whatever those two do not add up to is not lost -- it lands in reserves, because the identity current + capital + reserves = 0 is not a policy choice, it is bookkeeping. A "deficit" is just the name for the entry that reserves was forced to absorb.

Concepts: constraints, conservation.

An interactive you play with one thumb, on Wundr.