Pick a session from the dropdown to replay it, or set the
circuit/session fields by hand and press Load. Reachable two ways: visit this
server's own URL (it serves this page), or open the file from disk with `API`
pointed at a server (it sends Access-Control-Allow-Origin: *).
The dropdown lists every session OpenF1 knows for the year — not all are
archived yet, and a not-yet-archived pick replays as an empty track. /v1/circuit
is served entirely from F1's archive; /v1/location resolves its session via
OpenF1, so if OpenF1 is down or rate-limiting, set OPENF1_ARCHIVE_FALLBACK=true
and the cars still load. The track itself never needs OpenF1.