Game devs using the popular Unity engine face getting hit with a new fee every time a user downloads their game in a sudden, massive change to the engine's pricing model.

The change was announced in a blog yesterday. A new 'Runtime Fee' will be charged whenever a game is downloaded, provided it's already been installed a certain number of times and made a certain amount of money.

If you've been on social media at all in the last 24 hours, you've probably seen the backlash. Even if you haven't, you've probably heard the furious clacking of millions of angry keyboards. Unity tried to clarify things yesterday evening, but it hasn't really helped.

The reaction from devs has been apoplectic. RPS and IGN have roundups of negative comment from Devolver, Massive Monster, Innersloth, FrogteamGames, AGGRO CRAB, Feverdream (who dubbed the plans "psychotic") and The Cult of the Lamb devs who've threatened to delete their game entirely. And then of course, there's this from the Rust devs (language warning).

Eurogamer and Axios have the best write-ups I've seen, but here's a quick TLDR of dev anxieties:

• Free downloads are charged, so how does this affect spikes from demos, sales, giveaways, and GamePass? How can we be sure they'll stay profitable?

• What about multi-device users, and family sharing?

• Unity's clarification said charity bundles are exempt but... how? How do you distinguish different downloads? We don't understand the technical side of this and frankly it's scary you even have the ability to do it.

• Does this expose us to 'install bombing' where users can uninstall and reinstall a game, making us pay each time? (Axios received comment from Unity saying yes, then no)

• This is a fundamental change to the way you charge for your engine and you didn't consult us or tell us before now.

Ex-Fanatical BizDev manager Lewie Procter puts it neatly: "I haven't seen a single developer who is positive or even neutral on these changes. The list of devs Unity has alienated includes multiple GOTY creators... and that's just based on public statements. There will be many who are unable/unwilling to speak on this matter at this time."