the.com/difficulty curve
the slope between bored and rage-quitting, drawn on purpose.
means the planned rate at which a challenge gets harder as skill grows, ideally staying just ahead of you.
from borrowed from learning-curve psychology in the early 1900s, later formalized by game designers plotting player skill against challenge over time to keep people in flow rather than frustration.
flow zonenamed for csikszentmihalyi's balance of skill and challenge
spike dangersudden jumps cause most rage quits, not steady climbs
invisible tuninggood curves adapt live without players noticing
for instance
dark souls — deliberately brutal early spikes, 2011, taught patience as mechanic
candy crush — tunes per-level difficulty using real player failure data since 2012
portal — valve's 2007 tutorial-as-level design, near-zero frustration ramp
duolingo streaks — algorithmic difficulty scaling to keep daily users hooked