game-design-document

Abeceus System: Game Design Document

A tactical sci-fi TTRPG built for a digital VTT, emphasizing gritty realism, consequential combat, and smart play.

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Design Philosophy

Core Experience

The game should feel like a tactical milsim set in a hard sci-fi future. Combat is dangerous. Characters can die. But players who think tactically—scouting ahead, using cover, coordinating fire, employing the right tools—will survive and thrive. The goal is not to punish players, but to reward smart decisions and create genuine tension.

Players should feel:

• Relief and pride when they survive a combat encounter
• Tension when they know they’re walking into danger
• Agency over their survival through preparation and tactics
• The weight of their decisions—good and bad

Lethality Philosophy

One good hit can kill, but preparation protects.

• An unarmored character hit by a high-powered weapon dies or suffers catastrophic injury
• Quality armor, shields, and positioning create survivable situations
• Smart play (recon, cover, suppression, distractions) dramatically improves survival odds
• Reckless play against trained enemies is lethal—charging across open ground without protection should result in death

Weapon lethality scales realistically:

• Heavy weapons (railgun rifles, anti-materiel weapons) cause catastrophic, often irrecoverable wounds
• Standard firearms can kill, but wounds may be stabilized by skilled medics
• Headshots and heart shots are fatal regardless of weapon
• Location matters: gut wounds are survivable with treatment; CNS hits are not

Recovery follows realism:

• Field medicine stabilizes; real healing takes time
• A ship’s medbay can recover almost any non-fatal injury
• Without advanced medicine, characters suffer debuffs for realistic healing periods—or may die from wounds
• Lost limbs can be replaced with augmentation, but not in the field

Character Philosophy

No class restrictions—characters evolve freely.

Players define their character through a combination of:

• Stats (physical and mental attributes)
• Skills (granular competencies, grouped into categories)
• Traits/Perks (capabilities that change how you play)
• Equipment (gear defines tactical role as much as skills)

Characters are not locked into archetypes. An engineer can become a sniper. A medic can train into demolitions. Progression is player-directed.

Traits should feel meaningful:

• Avoid small numerical bonuses (+5% damage)
• Prefer capabilities that change playstyle (50% bonus headshot damage → “now I hunt for headshots”)
• Qualitative traits are ideal (thermal invisibility, breach expertise, zero-g combat mastery)

Physical stats can improve through training. Mental stats are more fixed.

Agency & Consequences

The system should not create unwinnable situations through randomness or GM fiat.

This is nuanced. Players should not always see danger coming—especially if they made poor decisions. If players fail to conduct recon when entering an area where they’ve been given reasonable clues that enemies could be operating, the GM is within their rights to spring an ambush.

What we want to avoid:

• Players in a “safe” location get ambushed by commandos and party-wiped in round one with no warning
• Players who anticipated a fight and positioned well lose a veteran to a lucky headshot
• Deaths that feel arbitrary rather than consequential

What is acceptable:

• Players who skip recon walk into an ambush they could have detected
• Reckless advances result in casualties
• Accumulated wounds and poor resource management lead to death

Morale/stress systems should provide warning before breaking points—players see it coming and can make decisions. Combat veterans get protective options even in ambushes. But consequences are real: characters can and will die from genuinely poor decisions.

Tactical Depth

Smart play is rewarded mechanically, not just narratively.

• Cover provides real protection
• Suppression restricts enemy actions
• Flanking creates vulnerability
• Ambushes are devastating (but work both ways)
• Recon (passive and active) reveals threats before they become lethal
• Equipment choices create tradeoffs (weight, volume, capability)

Resource Realism

Everything is tracked because the VTT makes it painless.

The digital platform allows granular tracking that would be tedious with pencil and paper:

• Ammunition (bullets, charges, fuel, missiles—not abstracted)
• Medical supplies (stimulants, biogel, bandages, surgical tools—not just “medkits”)
• Consumables (drone batteries, grenades, flares)
• Armor condition (plates/pads degrade and must be replaced)
• Carrying capacity (weight and volume, with tradeoffs for loadout)
• Ship resources (fuel, supplies, maintenance)

Players make meaningful loadout decisions:

• Combat pouches for essentials vs. packs for extended operations
• Heavy armor vs. mobility
• Specialized gear vs. versatility
• What to carry vs. what to leave on the ship

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Creative Direction: A Lived-In World

The World Reflects the System

The combat mechanics aren’t just rules — they’re a statement about what violence costs. The world itself should embody that. If the wound system says a gut shot is devastating, then there should be people walking around this universe who were gut-shot years ago and still carry it. If combat is terrifying, the culture should treat people who’ve been through it with a specific kind of weight — not glorification, not pity, just recognition.

The mechanics and the fiction validate each other. There is no invisible wall between the rulebook and the world.

People, Not Archetypes

The world is populated by real people, not stat blocks. The medic who knows exactly what an arterial bleed looks like and shows up anyway. The engineer keeping a ship running with parts that shouldn’t work together. The veteran who flinches at a door slam but still steps into the breach when it matters. The little species caught up in a resource conspiracy, finding ways to matter in a universe that doesn’t care about their scale.

Characters — player and NPC alike — should feel shaped by the world they live in: by the scars they carry, the things they own, the places they go, and the choices that got them there. The stories that matter most emerge from the bottom up, not the top down.

Asymmetric Encounters

The system is designed to be bedrock — a mesh that holds together any scenario, no matter how uneven. The most interesting fights aren’t mirror matches. They’re:

• A squad of under-equipped recruits against a single commando
• Civilians surviving a firefight they didn’t start
• A veteran with one working arm and three rounds left, making a stand
• Alien predators with inhuman silhouettes and no pain response
• Autonomous combat drones with no morale to break
• Mixed forces — human squads alongside robotic support against entrenched positions

This is where the channel-based action economy, geometric attack resolution, and wound system earn their complexity. Not when everyone has full resources, but when someone is fighting with half their channels degraded and has to think their way through it. Player creativity isn’t optional — it’s forced into existence by the situation.

Emotional Truth

Beyond simulation accuracy — beyond getting the ballistics and the armor penetration right — the system should produce moments that feel real. A player who survives a bad firefight should feel like they survived something, not just like they rolled well. Losing a character should hurt in a way that’s meaningful, not just annoying. The goal isn’t balance for its own sake. It’s truth: mechanical truth through physics and geometry, and emotional truth through consequence and weight.

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Turn Structure (Under Development)

Current Direction: Initiative with Protective Reactions

Core idea: Initiative-based turns, but characters can take limited Protective Actions outside their turn to avoid being helplessly exposed.

The Problem with Pure Initiative: In standard initiative systems, a faster enemy can move to flank a character who then sits motionless until their turn—unrealistic and frustrating. A commando shouldn’t be able to dash 90 degrees around a target while they stand still like a statue.

Protective Actions (proposed): When an enemy’s action would expose or endanger a character (flanking movement, incoming attack), the character may spend a Reaction to take a limited protective action:

• Drop prone
• Crouch behind cover
• Sidestep to maintain cover
• Raise shield

These don’t allow full movement or attacks—just reasonable self-preservation that a trained person would instinctively do.

Ambush Rules:

• Successful ambushes deny normal turns for the first round
• Combat veterans may take a single Protective Action (hit the dirt, dive to nearby cover)
• Non-veterans are caught in the open
• Ambushers get full actions with advantage

This needs playtesting to validate.

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Fog of War & Recon

Hidden Information

• Enemy positions are unknown until detected
• Detection requires line of sight, sensors, or successful recon
• Enemies can also fail to detect players—ambushes work both ways

Passive Recon

Some characters are more alert than others. High-awareness characters may:

• Notice environmental clues (disturbed ground, sounds, movement)
• Get “bad feeling” warnings before walking into ambushes
• Spot concealed enemies at greater range

This happens automatically based on skills/traits—no action required.

Active Recon

Players can choose to scout:

• Visual observation (binoculars, scopes, drones)
• Sensor sweeps (motion, thermal, EM)
• Overwatch positions (spotters calling out contacts)
• Drone reconnaissance

Active recon takes time and may reveal the scouts, but dramatically improves situational awareness.

Combat Veterans

Characters with significant combat experience:

• Habitually position near cover (better starting positions)
• React faster to ambushes (limited protective action)
• Higher passive awareness
• Stress immunity or high tolerance

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Stress & Morale

Design Goal

Stress should create tension and consequences without stealing player agency through arbitrary dice rolls. Players see it building and can make decisions—it’s not a surprise “you panic” moment.

Stress Accumulation

Stress points accumulate from:

• Taking fire (even misses)
• Taking wounds (severity matters)
• Seeing allies wounded
• Seeing allies killed
• Horrific sights
• Extended combat without rest
• Near-death experiences

Players can see their stress level at all times. Approaching a breakpoint is visible—players know they’re at risk.

Stress Thresholds by Experience

Experience Level	Breakpoint 1	Breakpoint 2	Breakpoint 3	Breakpoint 4
Raw recruit	20	35	50	65
Trained soldier	40	60	80	100
Veteran	70	100	130	160
Elite operator	Immune	Immune	150	200

Numbers are illustrative—to be tuned through playtesting.

Stress Reduction

• Rally: Leader uses action to reduce squad stress
• Fall back: Reaching safety reduces stress over time
• Stims: Chemical suppression (temporary, may have side effects)
• Rest: Extended rest between encounters clears stress

Agency Preservation

The key is visibility and choice:

• Players see stress building
• Players can pull back stressed characters before they break
• Players can have leaders rally the team
• Players can choose to push through at risk
• Breaking doesn’t happen “suddenly” from a bad roll—it happens when accumulated stress crosses a visible threshold

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Character Creation (Framework)

Attributes

Physical:

• Strength (carrying capacity, melee, physical tasks)
• Agility (movement, dodging, fine motor control)
• Endurance (stamina, wound tolerance, environmental resistance)

Mental:

• Perception (awareness, spotting, recon)
• Intelligence (technical skills, problem-solving, learning)
• Willpower (stress resistance, focus, morale)

Physical attributes can improve through training. Mental attributes are largely fixed.

Skill Levels

Skills use discrete levels (not 0-100 sliding scales). Each level represents a qualitative jump in capability, not a gradual improvement.

Level	Label	Description
0	Untrained	No formal training; rely on raw attributes
1	Novice	Basic training; knows fundamentals
2	Competent	Solid practitioner; reliable under normal conditions
3	Proficient	Experienced; handles stress and complexity well
4	Expert	Exceptional skill; recognized specialist
5	Master	Elite; among the best in the system

Design rationale: When a character levels up a skill, it should feel significant. Leveling from 2 to 3 is a real milestone—not just +2% to some formula. Each level may unlock new capabilities or breakpoints in addition to improving base performance.

Skill Groups

Characters have broad Skill Groups that cover related competencies. Within a group, related actions share competence—a rifleman can pick up an SMG and use it reasonably well.

Skill Group	Covers
Firearms	Rifles, pistols, SMGs, shotguns, mounted weapons
Heavy Weapons	Support weapons, launchers, emplaced weapons
Melee	Blades, bludgeons, unarmed, improvised
Throwing	Grenades, knives, improvised
Tactics	Squad coordination, breaching, ambush, defense
Engineering	Mechanical, electrical, structural
Software	Programming, hacking, AI systems
Electronics	Sensors, comms, ECM/ECCM
Demolitions	Breaching, traps, bomb disposal
Security	Locks, alarms, safes, countermeasures
Medicine	First aid, combat medicine, surgery
Pharmacology	Drugs, stims, poisons, anesthetics
Cybernetics	Installation, repair, diagnostics
Spacecraft	Small craft, capital ships, docking
Atmospheric Flight	Fixed wing, rotary, VTOL
Ground Vehicles	Wheeled, tracked, walkers
Drones	Recon, combat, utility
Persuasion	Negotiation, diplomacy, seduction
Deception	Lying, disguise, misdirection
Intimidation	Threats, interrogation, presence
Streetwise	Contacts, black market, criminal culture
Awareness	Observation, alertness, search
Stealth	Concealment, silent movement, camouflage
Navigation	Pathfinding, tracking, orienteering
Environment	Vacuum, toxic, extreme temp, zero-G

Specializations (Perk-Like Unlocks)

Specializations are not separate skills with their own levels. They are unlockable capabilities that enhance a skill group for specific applications.

How they work:

• You either have a specialization or you don’t
• Having a specialization grants bonuses/capabilities for that specific use case
• The specialization’s effectiveness scales with your base skill level
• Some advanced techniques require a specialization to even attempt

Example: Precision Shooting (specialization for Firearms)

A character with Firearms 3 and no specializations:

• Uses a sniper rifle competently at medium range
• Performance drops significantly at extreme range
• Cannot account for bullet drop, wind, breathing rhythm

A character with Firearms 3 + Precision Shooting:

• Full effectiveness at long range
• Can account for environmental factors
• Unlocks “called shot” techniques at extreme distance

A character with Firearms 5 + Precision Shooting:

• Master-level sniper
• Can make shots others consider impossible

A character with Firearms 5 and no Precision Shooting:

• Still better than Firearms 3 at long range
• But experiences significant dropoff compared to a specialist
• Cannot use advanced sniping techniques

Sample Specializations:

Skill Group	Specializations
Firearms	Precision Shooting, Rapid Fire, Close Quarters, Mounted Weapons
Heavy Weapons	Anti-Armor, Suppression Tactics, Indirect Fire
Melee	Blade Fighting, Grappling, Improvised Weapons
Tactics	Breaching, Ambush, Fire Team Leader, Zero-G Combat
Medicine	Trauma Surgery, Combat Stims, Field Prosthetics
Software	Intrusion, AI Manipulation, Cryptography
Spacecraft	Combat Maneuvers, Stealth Operations, Emergency Procedures
Stealth	Assassination, Infiltration, Counter-Surveillance

Traits/Perks

Beyond specializations, Traits provide unique capabilities that don’t fit the skill system.

Qualitative (new capability):

• Thermal Signature Masking: Invisible to thermal sensors when stationary
• Breach Expert: Can breach locked doors silently
• Zero-G Native: No penalties in microgravity
• Iron Constitution: Resistant to poisons and drugs

Quantitative but Impactful:

• Killer Instinct: Major bonus on finishing shots against wounded targets
• Iron Will: Double stress threshold before first breakpoint
• Quick Hands: Weapon swaps and reloads take half time

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Equipment & Loadout

Carrying System

Characters have:

• Combat Rig: Pouches, holsters, belt—always accessible, limited capacity
• Pack: Larger capacity, may be dropped in combat, affects mobility
• Armor Integration: Some armor has built-in storage

Weight & Volume

Every item has weight and volume. Exceeding capacity:

• Reduces movement speed
• Increases fatigue
• Imposes combat penalties

Armor System

• Armor has coverage (what body parts) and protection rating
• Plates/pads can be damaged and must be replaced
• Heavy armor protects better but reduces mobility
• Shields provide active protection but require power/attention

Weapon Categories

Category	Lethality	Notes
Sidearms	Moderate	Concealable, backup
Rifles	High	Standard combat weapon
Heavy Weapons	Extreme	Require strength/armor, devastating
Melee	Variable	Silent, no ammo, close range risk
Explosives	Extreme/Area	Grenades, breaching charges, rockets

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Scale of Play

Typical Encounter

• 2–6 Player Characters
• 0–4 Allied NPCs (under player or GM control)
• 2–20 Enemy combatants
• Total combatants usually under 20

Large Battles (Optional)

• GM may run larger engagements (up to ~100 per side)
• VTT automation handles NPC actions
• Players remain focus; battle is context

Campaign Structure

• Players have a ship, move freely through the system
• Manage supplies, fuel, money, reputation
• Missions at squad scale even during larger conflicts
• Vehicle and space combat rules (to be developed)

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Core Dice Mechanics

Design Philosophy

This game is built exclusively for a digital VTT. There is no need to optimize for:

• Physical dice rolling
• Mental math
• Memorizable formulas

Instead, we optimize for:

• Gameplay outcomes (formulas that produce the desired feel)
• Granularity (fine-grained modifiers the VTT calculates automatically)
• Transparency through UI (players see probabilities, not formulas)

Player Experience

Players don’t need to know the exact formulas. The VTT provides:

• A character builder that lets players experiment with builds
• Comprehensive stats pages showing how a character performs in various scenarios
• Real-time probability displays during combat (chance to hit, expected damage, etc.)

This allows us to use whatever mathematical structure produces the best gameplay, regardless of complexity.

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Hit Resolution System

The Body as Contiguous Mass

When a player aims at a body part, they’re not targeting an isolated hitbox—they’re aiming at a region on a contiguous mass. Near-misses can hit adjacent regions.

Example: Aiming for the eyes (small target, hard to hit):

• Success: Hit the eyes
• Near miss: Hit the head (still potentially lethal)
• Poor shot: Hit the torso
• Complete miss: Hit nothing

Example: Aiming center-mass at an exposed torso:

• Highest probability of hitting something
• But if only stomach-up is exposed (enemy in cover), probabilities shift

Attack Resolution Inputs

The algorithm considers:

Attacker factors:

• Relevant skill level
• Weapon accuracy and type
• Attack type (single shot, burst, aimed shot)
• Attacker status (wounded, suppressed, moving)

Target selection:

• Specific body region aimed at
• Size and position of that region
• Adjacent regions that might be hit on near-miss

Defender factors:

• Body layout (humanoid standard, armored, augmented)
• Armor and shields on each region
• Defensive stats (agility, size)
• Status (in cover, crouched, prone, moving)

Environmental factors:

• Range to target
• Visibility conditions
• Cover between attacker and defender

Resolution Output

The system determines:

1. Did anything get hit? (complete miss vs. some hit)
2. What region was hit? (intended target or adjacent region)
3. Was it blocked/mitigated? (armor, shields, cover)
4. What wound results? (severity, type, effects)

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Wound System

Core Concept: Wounds vs. Wound Effects

There is a critical distinction:

• Wounds are narrative descriptors: “.22 caliber gunshot wound to the left thigh” or “Acetylene torch burn on right forearm”
• Wound Effects are the mechanical impacts: bleeding, pain, impairment, stress

Wounds are tracked as single healable entities with a narrative description. Wound effects are the gameplay consequences drawn from a well-defined system. This allows varied, realistic injuries while keeping the mechanical impact manageable.

Wound Generation (Algorithmic)

Wounds are not selected from a lookup table. They are dynamically generated based on:

Inputs:

• Weapon characteristics (caliber, energy, damage type)
• Body region hit
• Armor/mitigation (reduced penetration = less severe wound)
• Hit quality (grazing vs. solid vs. critical)

Output:

• A narrative wound description
• A bundle of wound effects with severities
• Healing requirements

Example: A .22 pistol round hits an unarmored left leg.

Generated wound: “.22 caliber GSW, left thigh (muscle)”

Effects:

• Bleeding: Light
• Pain: Moderate
• Impairment: Limping (movement penalty)
• Stress: Moderate

Example: Same round, but target has light leg armor.

Generated wound: “.22 caliber GSW, left thigh (superficial, armor-mitigated)”

Effects:

• Bleeding: Minimal
• Pain: Minor
• Impairment: None
• Stress: Light

Wound Effect Types

These are the mechanical effects wounds can produce. A wound may produce several effects simultaneously.

Bleeding

Blood loss over time. Multiple bleeds stack.

Severity	Rate	Urgency
Minimal	Negligible	Self-resolving
Light	Slow drain	Minutes to address
Moderate	Steady drain	Needs treatment soon
Severe	Rapid drain	Immediate treatment required
Arterial	Critical	Seconds to unconsciousness

Blood Loss Track: Characters have a blood meter with breakpoints:

• 75%: Minor debuffs (weakness)
• 50%: Moderate debuffs (dizziness, reduced accuracy)
• 25%: Severe debuffs (near-collapse, impaired cognition)
• 0%: Unconsciousness → death

Pain

Imposes penalties mitigated by character toughness (Endurance).

Severity	Base Effect	Tough Character
Minor	Small penalty	Shrugged off
Moderate	Noticeable penalty	Small penalty
Severe	Major penalty	Moderate penalty
Overwhelming	Incapacitating	Major penalty

Physical Impairment

Functional limitations based on wound location.

Type	Cause	Effect
Limping	Leg/foot wound	Movement speed reduced
Arm impairment	Arm/shoulder wound	Penalty to actions using that arm
Hand impairment	Hand/wrist wound	Severe penalty to manipulation
Immobilized limb	Broken bone, tendon damage	Limb unusable
Lost limb	Traumatic amputation	Permanent (until augmentation)
Torso trauma	Organ damage	General debuffs, internal bleeding

Sensory Impairment

Type	Cause	Effect	Duration
Dazzled	Flash, bright light	Accuracy penalty	Short
Blurred vision	Blood in eyes, concussion	Perception penalty	Until cleared
Partial blindness	Eye damage	Severe perception penalty	Permanent
Full blindness	Both eyes destroyed	Cannot target visually	Permanent
Hearing impaired	Explosion, sonic	Communication/awareness penalty	Variable
Concussed	Head trauma	Penalty to all actions	Hours–days

Stress/Morale Impact

All wounds cause stress in addition to physical effects:

Wound Severity	Stress Impact
Minor wound	Light stress
Moderate wound	Moderate stress
Severe wound	Heavy stress
Near-fatal wound	Extreme stress

Critical/Fatal Wounds

Some wounds are immediately life-threatening or fatal:

Location	Unarmored Result	Armored Result
Head (CNS)	Fatal	Severe trauma, possible death
Heart	Fatal	Severe trauma, possible death
Spine	Paralysis or death	Severe trauma
Major artery	Fatal in seconds	Arterial bleed
Organ rupture	Fatal without surgery	Severe internal damage

Healing

Healing is also dynamic based on wound characteristics:

Wound Type	Field Treatment	Medbay Treatment	Natural Healing
Superficial	First aid clears	Quick	Days
Moderate	Stabilizes, debuffs remain	Full recovery	Weeks
Severe	Stabilizes only	Full recovery (slow)	Months
Critical	Buys time only	Possible recovery	Not possible
Lost limb	Stabilize stump	Augmentation required	N/A

Morale Breakpoints

As stress accumulates, behavior becomes restricted:

Level	Name	Effect
0	Calm	Full agency
1	Shaken	Unwilling to take risky maneuvers
2	Stressed	Unwilling to advance; will hold position and fire
3	Breaking	Will only take defensive actions; may freeze
4	Broken	Cowers, flees, or surrenders

Mitigation:

• Veterans have higher thresholds (or immunity)
• Rally actions from leaders reduce stress
• Stims can temporarily suppress effects
• Reaching safety reduces stress over time

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Open Questions

1. Turn Structure: Initiative + Protective Reactions needs playtesting
2. Exact Formulas: Mathematical structure for hit resolution, wound severity
3. Vehicle Combat: Separate rules needed
4. Space Combat: Ship-scale rules needed
5. Progression System: XP? Milestone? How do stats/skills/specializations improve?
6. NPC Stat Blocks: How simplified for GM ease?
7. Wound Interaction: How do multiple wounds compound?

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Next Steps

1. Draft mathematical formulas for hit resolution
2. Define complete wound type list with specific effects
3. Finalize skill groups and specializations
4. Design sample traits/perks
5. Create equipment lists with stats
6. Prototype combat encounter for playtesting

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See also:

• Raw Design Notes (Session 1)
• Raw Design Notes (Session 2)

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Combat Mechanics (Detailed Design)

Working document tracking all design decisions and open threads:

• Combat Mechanics — Working Document

Individual subsystem docs:

Subsystem	Status	Doc
Initiative & Turn Order	Decided	Initiative
Contact Phase	Decided	Contact Phase
Action Economy	Direction decided	Action Economy
Protective Actions & Reactions	Direction decided	Reactions
Attack Resolution	Direction decided	Attack Resolution
Wound System	Direction decided	Wounds
Visibility & Fog of War	Queued	Visibility

Simulation strategy:

• Simulation Strategy — Approach to automated testing, AI agents, and performance architecture

Sample encounters for playtesting:

• Basic 2v2 Encounter

Simulation outputs (auto-generated):

• Character Sheets — Reference characters with derived combat stats
• Sim Report — Latest Monte Carlo combat simulation results