It's very interesting, the TLDR is: (1) publish one or more blocks of data as inscriptions (2) these blocks can contain state changes e.g. they can move a native token from one address to another (3) publish a client that validates those state changes using the EVM

Boom: the EVM but on bitcoin

Some downsides:

• there is no 2 way peg, so the token on this rollup is some sort of altcoin (could be a 1 way peg though)
• the only reason that rollup data gets dumped onto bitcoin is because rollup users don't want to host that data, which is stupid