This Game Is Free If You Unlock an Achievement in Another Dev's Game

A new, procedurally generated shooter called Polygod debuted this week on Steam in early access. It's described as a roguelike that drew inspiration from The Binding of Isaac. Its developer believes fans of it will enjoy Polygod, so it's giving the game away for free to those who earned certain Achievements in Isaac--a game it didn't make.

"I really loved The Binding of Isaac and I think Polygod will resonate well with players that also really enjoyed The Binding of Isaac," said Amplify Games co-founder Dominic Obojkovits. "Because of this, I want to reward the most dedicated players with a copy of Polygod."

Plans to do this were first announced in September but are now gaining more attention now that Polygod is out on Steam, where it goes for $10 ($9 until October 20). Achievements from both The Binding of Isaac and The Binding of Isaac: Rebirth qualify. You can see the full list of eligible ones below--you only need to have unlocked one to earn a copy of Polygod.

The Binding of Isaac Achievements

• Hard Game
• Eternal Satan
• Eternal Cain
• Eternal Isaac
• Eternal ???
• Eternal Maggy
• Eternal Eve
• Eternal Samson
• Eternal Judas
• Eternal God
• Eternal Personalities

The Binding of Isaac Rebirth Achievements

• Sticky Nickels
• Keeper now holds… A Penny!
• Keeper holds Store Key
• Noose Baby
• Karma
• Sale Baby
• Mega
• 1001%

As you might assume, these aren't common Achievements--Amplify chose the least-unlocked ones from both games. Hard Game is most common among those from The Binding of Isaac, and that's only been unlocked by 1.1 percent of players on Steam. Rebirth's have been more frequently unlocked, ranging from 3 to 4.8 percent of players.

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The process for getting your free game isn't automated. If you've unlocked any of these yourself and want Polygod, add Amplify's Steam account, Atomicdomb, and send it a message from the account with the qualifying Achievement. The developer will check your account and "respond accordingly."