Every roguelike has a difficulty curve, even if the designers haven't drawn it explicitly. It's the line your average player traces from "I have no idea what's happening" to "I can clear a run blindfolded." How you shape that line is the single biggest variable in whether players bounce or stay.
There are two common failure shapes, and most games slip into one of them by accident.
The cliff
The cliff is the curve where the first ten hours are brutal and the next fifty are trivial. New players die to room three on their second run because they haven't learned the enemy patterns, the resource economy, or the synergy that makes the build viable. They never make it to the bit where the game opens up. The community that does push past the cliff develops a culture of git gud in self-defence, which doesn't help anyone arriving later.
The cliff is usually unintentional. It tends to come from designers and playtesters who already know the game cold — every system feels intuitive to them because they built it. The curve they ship is the curve they experience, which is flat from day one.
The ramp
The ramp is the opposite. Twenty hours of slowly escalating challenges where every run feels broadly the same — slightly harder enemies, slightly bigger numbers. Veteran players hit a wall not of difficulty but of sameness. They beat the final boss, they shrug, they uninstall.
The ramp comes from designers who over-correct for the cliff. "We want this to be welcoming" turns into "every system unlocks late so nobody is overwhelmed early" which turns into a fundamentally flat game where the cool stuff lives behind a hundred hours of progression. Roguelikes are particularly vulnerable to this because the meta-progression mechanic invites it.
What the good curves look like
The games that hold players for hundreds of hours — Slay the Spire, Hades, Balatro, FTL, the modern Mystery Dungeon entries — all share a curve shape: steep but climbable on the first run, with sudden spikes of difficulty unlocked by player choice.
"Steep but climbable" means a new player can finish a run in their first few attempts if they're paying attention. Not because the game is easy, but because the early floors teach the systems explicitly and the failure modes are obvious. You died because you went into the elite fight at 30% HP — not because the elite had a hidden weakness you couldn't have known about.
"Sudden spikes unlocked by player choice" means the game can become much harder, on demand, at the level the player picks. Ascensions in Slay the Spire. Heat in Hades. Stake levels in Balatro. The player who's bored of the base game opts into a harder one without anyone asking them to grind first.
Two design tools that actually work
First — asymmetric optional content. Most rooms have a base challenge level. A small number of rooms are dramatically harder and offer dramatically better rewards. Players pick their own difficulty within a single run by choosing whether to engage. New players avoid them and learn the base game. Veterans seek them out and learn the edge cases. Same content, two audiences, no scaling code needed.
Second — opt-in modifiers. The post-victory unlock isn't "you can now play floor 11"; it's "you can now start a run with a curse that does X." Players choose how much harder they want their next run to be. They're never forced into a difficulty level above their preference, which means nobody bounces off the wall.
What doesn't work
Scaling enemy stats with player level — adding 5 HP to every enemy because the player picked up a +5 damage item — is the cheapest possible solution and it has fooled exactly nobody. Players feel the scaling and resent it. If they push through it anyway, you've wasted everyone's time: their build feels useless, your encounter design has no shape, and the win at the end of a level-scaled fight feels weightless.
If you need the late game harder, change the composition of encounters rather than the stats inside them. Add new enemy types, new room layouts, new modifiers — anything where the player's response to difficulty is "I need a different strategy" rather than "I need bigger numbers."
Test with strangers
If you take one thing away from this: put your game in front of someone who's never played it, watch them silently, and write down every single thing they do that surprises you. They'll bounce off a wall you didn't know was there. They'll skip a tutorial you thought was obvious. They'll find a strategy you'd never considered.
The difficulty curve you ship is the curve strangers experience. Yours doesn't count.