PROC RATES
Percentage chances for effects to trigger on actions — 15% chance to freeze on hit, on-kill explosion procs, critical effects with per-hit odds — 'proc' being the MMO-era term for programmed random occurrences.
- SOLO-DEV COST LOW
- TIMING REAL-TIME / TURN
- COMMON IN MMO · ARPG · MOBA · LOOTER-SHOOTER
World of Warcraft built rotation depth on weapon and trinket procs (reacting to the proc is the skill), Path of Exile and Warframe turn proc chance into buildcraft's central mathematics (status chance times hit rate times effect stacking), Slay the Spire-likes print card effects with trigger odds, and every ARPG's on-hit affix pool is proc design at industrial scale. Designers use procs because they inject variance into repetitive actions at near-zero cost: the thousandth sword swing is identical to the first, but a 10% freeze proc makes each swing a lottery ticket, and the intermittent reinforcement schedule — the same one slot machines run — keeps attention alive through repetition. Procs also create reactive gameplay (the proc lights up, the rotation changes) and multiplicative build depth, since proc chance, attack speed, and effect power form optimization triangles theorycrafters live inside. Key decisions: true randomness versus pseudo-random distribution (Dota 2's PRD raises the chance after each miss, taming streaks — the difference between statistics and felt fairness), whether procs can chain or nest (proc-ception is where degenerate builds breed), and visibility — a proc the player doesn't notice fired is design spent on nothing. Pitfall: builds balanced around proc averages that play as feast-or-famine — a 20% proc that the build needs every fight will fail four fights in a row somewhere, and the player experiences not variance but betrayal; effects load-bearing enough to build around need floors, pity timers, or PRD smoothing.