ICRPG Core Mechanics - Targets, Effort, Hearts and Timers

⚙️ The Core Rules in a Few Lines

ICRPG keeps its rules small enough to fit on an index card. Everything at the table comes back to these pieces:

The attempt: roll d20 + the relevant stat (STR, DEX, CON, INT, WIS or CHA) and try to meet or beat the room's Target — one number for everything in that room, often around 10–14.
EASY and HARD: an easy task is Target −3; a hard one is Target +3. In a Target 12 room with no bonus, that's 60% (EASY, 9+), 45% (normal, 12+) and 30% (HARD, 15+).
Natural 20 and natural 1: a natural 20 is a critical success with an extra-big effect; a natural 1 is a fumble that makes things worse.
Effort: after a successful attempt, roll an Effort die to make progress or deal damage — Basic d4, Weapons & Tools d6, Guns d8, Energy/Magic d10, Ultimate d12.
Hearts: 1 heart = 10 HP. Heroes typically start with 1 heart; monsters and big obstacles are measured in hearts too.
Timers: a countdown die or a set number of rounds — when it runs out, something happens.

The sections below look at each piece in turn. When you’re ready to build rooms that put them to work, the D.E.W. method in Room Design shows how to give every room Danger, Energy and Wonder.

🎯 Core Mechanics and Target Numbers

ICRPG operates on elegant simplicity—roll a d20, add your stat, meet or beat the Target. Each room or scene has ONE Target number (often around 10–14) that the GM sets for everything there; easy and hard tasks just shift it. Like a well-tuned engine, every component serves a clear purpose without unnecessary complications.

One Target per Room

TARGET - set per room

One number for every attempt in this room or scene, often around 10–14

EASY - Target −3

Simple tasks, favorable conditions, good tools or a clever plan

HARD - Target +3

Challenging tasks, unfavorable conditions, bad footing

NATURAL 20 / NATURAL 1

A natural 20 is a critical success with a big effect; a natural 1 is a fumble that goes badly

The chart below shows your chance to succeed in a room with Target 12: EASY attempts need 9 or more, HARD attempts need 15 or more. Each +1 of stat bonus adds 5%.

💪 The Effort System and Combat Flow

ICRPG's effort system creates combat that flows like a river rapids—fast, exciting, and always moving forward. Instead of calculating complex damage formulas, heroes roll effort dice that represent their training, equipment, and determination.

graph TB A[Roll d20] --> B[Add Stat] B --> C[Meet or Beat Target] C --> D[Roll Effort] D --> E[Apply Damage/Effect] F[Weapon Effort] --> D G[Energy/Magic Effort] --> D H[Ultimate Effort] --> D style A fill:#FF6B35 style D fill:#4ECDC4 style E fill:#45B7D1

Effort Die Types and Meanings

d4 Effort - Basic

Fists, improvised weapons, makeshift tools, general hard work. Reliable but limited impact, like a steady drizzle that eventually fills the bucket.

d6 Effort - Weapons & Tools

Swords, bows, axes, lockpicks, toolkits. The bread and butter of adventuring, consistent and effective.

d8 Effort - Guns

Pistols, rifles, blasters. Firearms hit harder than blades.

d10 Effort - Energy/Magic

Spells, prayers, psionics and energy powers. Represents serious training and power beyond the mundane.

d12 Effort - Ultimate

Artifacts, ultimate techniques, legendary abilities. Loot and abilities add bonuses on top of all these dice. The stuff of heroes and legends, reshaping entire encounters.

♥️ Hearts: Hit Points in Tens

The Heart System

ICRPG measures health in HEARTS. Each heart = 10 HP: you still subtract Effort from hit points, but you size every creature in hearts. Heroes usually start with 1 heart. Simple, visual, dramatic.

Ogre Chieftain: 3/5 Hearts

Why Hearts Work

Visual tracking (use tokens!)
Easy math (no 37 HP monsters)
Dramatic moments ("Last heart!")
Scales elegantly

Enemy Heart Guidelines (this guide's rough tiers; see the Monster Bestiary)

Minions: ½ heart (5 HP; one or two solid hits drop them)
Regular foes: 1-2 Hearts
Elites: 3-4 Hearts
Bosses: 5+ Hearts

⏳ Timers and Escalating Tension

ICRPG uses timers like a master storyteller uses pacing—creating urgency and driving action forward. Every tick of the timer raises stakes and forces heroes to make bold decisions rather than endless planning.

Timer Applications

Combat Encounters

Reinforcements arrive, the building collapses, the bomb explodes—timers ensure fights end decisively rather than dragging into stalemates.

Exploration Challenges

Rising water, pursuing enemies, spreading poison gas—environmental hazards that force quick thinking and bold action.

Social Situations

The king loses patience, the crowd turns hostile, the merchant gets a better offer—adding urgency to diplomatic encounters.

🚪 Rooms and Milestones

ICRPG structures adventures like perfectly paced action movies—each room or scene presents clear challenges, meaningful choices, and tangible progress toward the ultimate goal.

Essential Room Elements

Clear Objective

Every room has an obvious goal—defeat the guardian, solve the puzzle, rescue the prisoner. Heroes always know what success looks like.

Interactive Elements

Levers to pull, doors to break, traps to disarm. The environment becomes part of the tactical challenge rather than passive scenery.

Timer Pressure

Something forces action—collapsing ceiling, approaching guards, spreading fire. Standing still equals failure.

Meaningful Reward

Progress toward the goal, useful loot, important information. Loot is ICRPG's main reward and, together with milestones, the main way heroes grow.

🏆 Key Takeaways

🎯 One Target per room: roll d20 + stat and meet or beat it; EASY is Target −3, HARD is +3
💪 Effort measures how much you get done: d4 Basic, d6 Weapons & Tools, d8 Guns, d10 Energy/Magic, d12 Ultimate
♥️ Hearts: 1 heart = 10 HP; heroes usually start with 1
⏳ Timers turn waiting into urgency: when the countdown ends, something happens
🚪 Rooms and milestones keep play moving forward, with loot and progress as the reward