Every 5 consecutive direct hits increases your multiplier (up to ×5); misses break it. Collect refills or 4-second shields. Clear every enemy to finish each wave, then take a 3-second breather. Hits charge the COPIUM BOMB; press SPACE or tap its button when ready to clear runners and deal 10 boss damage. Hit a runner: +2% COPIUM. Missed shot: -2% COPIUM. Runner escapes: -7% COPIUM. Runners speed up each wave. Move your cursor to aim the Gjallarhorn. Every 10th hit unleashes Wolfpack — they can hit runners AND the boss. Boss kill gives +10% COPIUM. Boss shots take 12% COPIUM. Reach 0% COPIUM and it's GAME OVER.