An orbit, once cast, is a promise: everyone can compute where a thrown payload will arrive, months out. So the war is fought over mass, not position — real slugs fly among balloon decoys with matched signatures, and the defense must commit before it can tell them apart.
The mass-driver rail on Mars charges across each minute and fires at :00 — the rail is the second hand. One payload per minute rides the corridor; at the discrimination line the balloons deflate and the slugs harden; past the commit ring the defenders sortie. The tally ring around Earth is the hour: one mark for every hour's slug that got through.
Displays viewer-local civil time. Cease fire pauses the battle while the clock keeps reading. Ship sprites by RavenmoreArt (dycha.net) under the included royalty-free license; Earth texture NASA Blue Marble. A clock from datapoems.io/clocks/ by Luke Steuber. MIT.