Skill-based XP

tim-cain game-design xp-systems skill-systems rpg-design progression balance

Abstract

Problem: If an RPG awards XP directly to skills when they're used, what design problems emerge and how should designers handle them?

Approach: Tim Cain walks through the practical consequences of skill-based XP systems, drawing on his experience shipping RPGs and observing player behavior in games that use this model.

Findings: Skill-based XP creates numerous exploitability and balance issues — from grinding low-level enemies to camping NPCs for persuasion XP. Designers must carefully define what "using a skill" means, balance XP rates across skills with wildly different usage frequencies, and decide whether levels and hit points still exist. A compelling alternative: award XP only on failure, which naturally encourages players to seek challenges rather than grind easy content.

Key insight: XP is the designer's most powerful currency for shaping player behavior — awarding it on skill failure rather than success creates a self-balancing system that encourages players to seek challenges instead of grinding.

Source: https://www.youtube.com/watch?v=AK5nnqOCaCg

1. Context

This video is a follow-up to Tim Cain's earlier video on the best way to give XP (spoiler: quests), which generated significant community discussion. He also references his video on class-based vs. skill-based systems. Tim emphasizes he's not telling designers not to use skill-based XP — he's identifying the problems they'll need to solve if they choose this approach.

2. What Is Skill-based XP?

The basic concept: whenever you use a skill, you gain a small amount of XP for that specific skill. Each skill has its own XP bar. When the bar fills, the skill levels up (numerically, or from beginner to expert, etc.), the bar empties, and you refill it by using the skill again.

Tim notes this applies broadly — not just to skills, but to any progression system where the player selects something (perks, traits, backgrounds, attributes) that subsequently determines outcomes in the game.

3. Problem 1: What Does "Using a Skill" Actually Mean?

This seems obvious but gets complicated fast:

  • Combat skills: Does swinging a sword at barrels count? What about non-hostile creatures? If XP only comes from hostile enemies, does a stealth one-hit-kill count (the enemy never became hostile)?
  • Stealth: Does just sneaking around give XP? Do you need to attack? If sneaking near unaware NPCs grants XP, players will sit in a bush behind a low-perception guard and farm stealth XP indefinitely.
  • The definition problem: Designers must express these rules precisely enough for programmers to implement. Vague notions like "meaningful use" don't translate to code.

Tim points out that if guards or locks have limited XP to give (like a stealth XP pool per NPC), you've added significant programming complexity — and you'd better communicate to the player when that pool is exhausted.

4. Problem 2: Usage Frequency Imbalance

Combat skills get used vastly more often than other skills. You swing a sword 10–30 times per combat encounter, but you pick a lock once. Without intervention:

  • Combat skills will hit max almost immediately
  • Lock-picking and persuasion will take weeks of play to level up

Possible mitigations: larger XP bars for frequently-used skills, or diminishing returns per use. But creating a fair, balanced-feeling system across all skills is "tricky and time-consuming."

5. Problem 3: Encouraging Degenerate Play

Skill-based XP encourages players to:

  • Run around low-level areas fighting rats until combat skills are maxed
  • Cast Fireball at walls repeatedly to raise magic skills
  • Jump off walls repeatedly for acrobatics XP
  • Camp in front of a shopkeeper whose persuasion dialogue resets every 24 hours, persuading them over and over
  • Summon creatures just to fight them in a room

Tim asks pointedly: "Is this really how you want play guides to describe your game?" Because XP is the designer telling the player this is what I encourage you to do.

6. Problem 4: Levels, Hit Points, and Encounter Design

If skills progress independently, does the player even have a level? Many tabletop RPGs (like GURPS) don't use levels. But removing levels raises hard questions:

  • How do encounter designers determine appropriate challenges when skill progression is haphazard and player-driven?
  • When or how does the player gain hit points?
  • Do you start and end the game with the same hit points?
  • How does your combat system work if power progression is non-linear?

7. The Failure-based XP Alternative

Tim's most provocative suggestion: award skill XP not when you use a skill, but when you use it and fail.

7.1. Why This Works

  • Natural feeling: People learn more from failure than success. When you succeed, you often don't know why. When you fail, you almost always know why.
  • Enables generalist builds: If you try many different things with low skills, you'll fail at all of them — and all those skills will go up.
  • Specialization requires investment: To specialize, you must find many instances of a skill challenge and keep failing at them until you improve.
  • Self-balancing: If you're always succeeding at a skill, you don't need it to go higher. If you're failing, you're gaining XP. The questions answer themselves.
  • Encourages seeking challenges: Players are incentivized to find hard combat, difficult locks, and tough persuasion checks — because those are the things they'll learn from. No more sitting in sewers killing rats.

8. Core Principle

XP is the most powerful currency a designer has. Every time you award XP, you're telling the player: "This is what I encourage you to do." Skill-based XP systems will shape player behavior — the question is whether you're shaping it in the direction you actually want.

9. References