IMO as ethical as ads, it just shouldn't run on mobile and laptops not connected to power. Otherwise I'm happy to run cryptominer from YOUR domain as long as I'm browsing your domain.
The income was abysmal and it never felt quite right, even though I clearly prompted the user that I would use their CPU when they clicked "Mine". Since Coinhive shut down the game no longer works but here's an article about it: https://btcmanager.com/tombs-io-launches-collaborative-onlin...