Neon Unicorn Frappuccino

You write simulations where the interesting behavior is supposed to come out of the dice rather than be animated by hand.

Build me a single HTML page: a Starbucks-style coffee shop running a bizarre promotion, simulated live.

The build

• Customers are simple circles or dots. They line up outside, enter the shop, order, receive a drink, and leave. At most 8 customers are inside at once; the rest wait in line.
• Every Frappuccino sold has an independent 1-in-6 chance of coming out as a glowing Neon Unicorn Frappuccino in psychedelic colors. Roll it per drink, at the counter, and let nothing else decide it.
• Track how many customers currently inside the shop are holding a Neon Unicorn. The shop reacts to that count:
  • 1: a subtle neon glow, or some small wrongness in the picture.
  • 2: an increasingly unstable coincidence — flashing lights, a shaking building, particles, warped colors.
  • 3 or more: the catastrophic NEON Unicorn EVENT. Go completely overboard: the shop collapses, explodes, mutates or otherwise fails spectacularly, and a giant dancing neon Unicorn creature emerges.
• After the catastrophe the shop resets or rebuilds, and the simulation carries on.
• No scripted catastrophe. No timer, no quota, no loaded die that makes an event arrive on schedule. An event happens because three unicorns were in the room at once and for no other reason. If you nudge the odds anywhere, say so in the notes.
• Live statistics: customers served, Neon Unicorns produced, the observed unicorn rate beside the true 1-in-6, catastrophes, and any other amusing metrics you invent.
• A control for simulation speed, so I can fast-forward to the next disaster.