Balancing section length and mistake tolerance

How long should levels or sections be? And how many mistakes should the player be able to make without losing; how many hits should enemy take to kill them?

Concept of sections

These questions are closely related; the answers depend on each other. If a game has very short distances between checkpoints, like Celeste or Katana Zero, it's okay if the player dies in one hit from anything, since they won't be losing much progress. But in a game where save points can be several minutes apart, like most RPGs, it'd be extremely frustrating if you could lose that much progress to one mistake.

I can't give an exact ideal ratio, but it's worth looking at some examples:

In Celeste and Katana Zero, checkpoints are maybe 10 seconds apart on average (estimate; I played them long ago).

Cuphead is a game where most bosses are about 2 minutes long, and you have 3-5 hits depending on equipment. I personally felt Cuphead should've been balanced for a bit more HP.

Hollow Knight has, I think, similar boss length, and you have 5-11 HP depending on upgrades (with a few enemies dealing double damage), plus the ability to heal. But Hollow Knight sections aren't always just a boss fight; there's exploration, arena fights with waves of enemies that can be several minutes long, boss rushes, etc.

Undertale save points are generally several minutes apart, and you can take something like 4-7 hits from different attacks (again, estimate), and you have healing items. But because it's turn-based, unlike Hollow Knight, you don't need to find a safe window to heal; you get a chance to heal every turn, until you run out of healing items.

I don't have any good examples of games with longer sections than that.

But the ratio between these two things isn't the only thing to consider. The number of mistakes a player should be able to survive also depends on how easy they are to make. If the screen is full of enemy projectiles, each one should do less damage than if there's just one enemy attacking slowly. You can think of it as an *amount of mistake* rather than a *number of mistakes* that should lead to failure.

Longer sections or levels also make it more of a time commitment to play one, meaning players find fewer opportunities to play the game. That doesn't mean there's no space for games with long sections, though. Longer sections allow more state and more strategic dynamics to exist within them. For example, in a game with one-hit kills and 10-second challenges, you can't have those intense moments where you're close to winning but also close to dying. You can't have strategies that involve a short-term sacrifice for long-term gain.

Final Fantasy 13 is a bad example of a game with long sections. It uses the encounter-section model of saving, meaning sections are just individual fights, but the individual fights can be very long: some bosses took me *20 minutes* on my winning attempt, and in this case, that length isn't being used to make room for any strategy; most of the time is just spent repeating the same actions. The game would've been more fun with enemy health drastically reduced.