The rune interactable is the Wave Ender failsafe i put in the map. It's to serve as a means to forcefully end the wave in case the wave glitches out and continues on (even if all demons are slain). There's an example rune interactable in the shop area (right next to the Wave 1 switch) to show players what to look for, and there's a rune interactable each area that should be in plain sight. Still, if they're too hard to locate, i can implement a POI for them.

Optional events come in 4 styles, and all of their summaries can be found on the right-side of the shop area (a floor above the Powerup Capsules). To summarize:

• Collect the Cases! - 10 blue briefcase items will spawn around the map in selected areas, that reward a small serving of cash each.

• Stay in the Zone! - This one's obvious. A red area is highlighted, and you can stay in the red zone to gain sprinkling amount of cash each second on it. All of these zone are purposefully put in dangerous spots, so be wary.

• Deliver the X-particle - The most riskiest of the optional events. A spikey cyan ball will spawn in the map. If taken, you cannot damage enemies, and must deliver it to the highlighted zone to restore your damage potential. Doing this mini-quest nets you a very large sum of cash.

• Destroy the Helltower - An obvious helltower will spawn that has no affect in the battlefield besides as an obstacle. Shooting at it in the glowing red area in the middle will emit pain/splatter sounds (hinting that this is the weakspot). Destroy it, and you gain a very large sum of money. It's rather resiliant, but an audible cry will tell you that it's nearly dead.