The Game Engine Behind Slay the Spire 2 Is a Game-Changer

These days, many major games require a purchase to play, but the developers of Slay the Spire 2 have completely flipped that trend on its head. The secret lies in the game’s engine.

In simple terms, a game engine is the software that developers use to create their games. By 2024, the team at Mega Crit had already invested two years into developing the roguelike using Unity, a well-known engine behind hits like Among Us and Hollow Knight. However, when Unity announced plans to charge developers for every download, Mega Crit pivoted and began building Slay the Spire 2 on Godot.

While Godot may not have the same recognition as Unreal Engine 5, it offers some distinct advantages. One of the most significant is that it’s open-source, which means Slay the Spire 2 is also open-source. This allows anyone with the right skills to dive into the game’s source code and see how it was constructed.

This is a remarkable situation. As of now, Slay the Spire 2 is set to be one of the biggest game releases of 2026, and anyone can explore its creation process. Typically, access to a game’s source code is rare and often comes years after launch, if it’s released at all. In fact, many developers and publishers have lost their source code entirely, as seen with several retro titles that weren’t preserved.

Another interesting aspect of Slay the Spire 2’s Godot foundation is that the open-source nature makes it easier for the game to be distributed without payment. Almost immediately after its launch, the early access title appeared on piracy sites. While many developers would be concerned about the unauthorized sharing of their work, Mega Crit appears unfazed by the piracy surrounding Slay the Spire 2.

In a Reddit discussion where someone inquired about preventing asset theft, Mega Crit’s lead programmer, Jake Card, offered a surprising take. “Honestly, we don’t really,” Card stated. “We figure people who want to pirate it will find ways to pirate it, so there’s no reason to waste dev resources on it.”

In another thread, when a user noted that anyone could decompile Slay the Spire 2 to access its source code, Card expressed his approval. “It’d make me extremely happy to find out that other game developers learned something from reading through our code and our scenes :),” he replied, highlighting the potential benefits of the game’s open-source design for fellow developers.

Earlier this year, Card elaborated on how Mega Crit viewed Godot’s open-source framework as a significant advantage. During the transition from Unity to Godot, they could troubleshoot issues by examining the Godot engine itself. Ultimately, Mega Crit created a custom version of the engine tailored to meet the specific requirements of Slay the Spire 2.

“The open-source aspect remained a huge advantage as we got further and further into production,” Card noted. “We never hit the sort of ‘dead ends’ you can encounter with Unity when you just can’t find a solution to your problem.”

Even with the option to download Slay the Spire 2 for free, there are still compelling reasons to purchase it. For some players, it’s about supporting a developer who has created an addictive game. For others, buying the game makes sense because the pirated version lacks multiplayer support, which includes its own unlockables and characters.