I spent this
@monad metropolis hackathon on Interlude, which is the Ephemeral Rollup
Kanddle is the app I built on it so you can watch the idea work, instead of reading a diagram.
The game is simple, two people open a 1v1 on Monad, lock the same stack, and tap squares on a tape. If the print hits your square you score. If it misses, you do not. When the clock ends, the higher stack takes the pot.
Do that on a chain the usual way and every tap is an L1 transaction. Even if the wallet is quiet, you still pay gas, you still wait on a block, and you still do not get the result back in the same breath. Twenty taps in ninety seconds becomes twenty confirmations. The match cannot live there.
Do that on a server and the match is instant, because the server is just editing a row. It can ignore a tap, rewrite a stack, or vanish and take the room with it. The chips may sit in a contract. The fight does not. You are trusting whoever runs the box.
The Ephemeral Rollup is the third path. Same Solidity, same address. You sign a session once. After that each tap is a real contract call on the node, both players share that state, and the node later commits the net diffs back to Monad. Fast while you play. Settled when it counts. If the node lies, the batch is replayable and the bond is there. v1 is still permissioned. I am not pretending otherwise.
That is why Kanddle exists. I needed a live room two people can actually play, and I needed the pot to stay in the contract they already deposited into. A raw chain breaks the room. A server breaks the pot. Interlude is the ER that lets both stay true.
The app is rough. Plenty still broken. If you want early access, say so in the comments.