Pyromancer's Goggles + Expansion // Explosion

Prerequisites

You have an additional instant or sorcery card in hand with mana value 4 or less.

Steps

1. Cast any instant or sorcery with mana value 4 or less by paying its mana cost.
2. Holding priority, activate Pyromancer's Goggles by tapping it, adding {R}.
3. Cast Expansion by paying its mana cost, targeting the instant or sorcery cast in step 1.
4. Pyromancer's Goggles triggers, copying Expansion, with the copy targeting the original Expansion.
5. Resolve the copy of Expansion, creating a copy of Expansion targeting the original Expansion.
6. Repeat step 5.