Stealth Detection System

1. Summary

A layered stealth detection system governing how enemy guards and civilians perceive player characters. The system combines three sensory channels: visual (cone-shaped vision fields projected in world-space with color-coded states), auditory (noise radii from movement, abilities, and combat that prompt investigation), and environmental (snow footprints, darkness, and torchlight altering visibility). Detection progresses through three states — undetected, suspicion, and alert — with full detection triggering alarm responses, additional patrols, and potential mission failure. Players manage detection risk through stance (crouching vs standing), movement speed, concealment spots, body hiding, and distraction abilities.

2. Tags

3. Design Intent / Job Story

When planning a route through enemy-patrolled territory, I want to see exactly where guards are looking and hearing, so that I can time my movement and abilities to remain undetected.

4. Role in Gameplay Loop

• Provides the core risk loop of stealth gameplay: every enemy is a moving puzzle of sight and sound
• Drives tactical decision-making about pathing, timing, and ability use
• Creates tension through progressive detection states that give the player a brief window to recover before failure
• Enables environmental storytelling via snow footprints, torchlight, and darkness altering patrol behavior
• Supports the save-scumming iteration loop by making detection consequences severe but rewindable
• Rewards cross-character coordination (e.g., one character distracts while another slips through a blind spot)

5. Preconditions

• The mission level has loaded with active enemy and civilian NPC placements
• Enemy patrol routes and initial facing directions are defined by level design
• At least one player-controlled character is alive and not incapacitated
• The player has visibility of enemy vision cones (default UI state)
• Environmental conditions (day/night, snow, torch presence) are set per level configuration

6. Parameters

7. Core Rules

• Every enemy and civilian NPC possesses a visible vision cone projected in world-space aligned to their facing direction and patrol state.
• Vision cones use color coding: green indicates the player is undetected, yellow indicates detection buildup, and red indicates confirmed detection.
• Detection progresses through three states: Undetected → Suspicion (question mark icon above the enemy) → Alert/Detected (exclamation mark icon).
• A player character inside a vision cone is spotted based on stance (standing vs crouching), movement speed, and proximity to the cone origin.
• Crouching characters in the outer portion of a vision cone remain undetected; standing or running characters are detected faster.
• Each enemy type applies distinct detection modifiers: normal guards use baseline values; straw hat guards observe a wider area and can spot projectiles in flight; samurai see through disguises.
• The auditory layer evaluates noise events — footsteps, combat, ability usage, and environmental sounds — within a radius around each enemy.
• Noise-producing actions display a blue circular radius during targeting; enemies within that radius stop their current behavior and investigate the sound source.
• Character movement produces varying footstep noise: some characters are silent when running, others produce standard or elevated noise levels.
• Snow-covered ground leaves temporary footprints that enemies can detect and follow; footprints fade automatically over time.
• Darkness reduces enemy vision range; torch-carrying enemies create localized bright zones that restore or extend vision within the light radius.
• Bodies of slain or unconscious characters trigger detection if visible to any enemy or civilian; hiding bodies in concealment spots (bushes, rooms, barrels, wells) prevents discovery.
• Full detection of a player character triggers the mission alarm state, spawning additional patrols; if the character is caught within melee reach, the mission fails immediately.
• Detection state resets per character when line of sight is broken and the enemy completes their investigation cooldown, but alarm-level consequences persist until the mission is reloaded or completed.

8. BDD Scenarios

9. Edge Cases

• A player character carrying a body may be spotted at a greater distance or through partial cover than when unencumbered
• Two enemies with overlapping vision cones can detect a character in the intersection faster than either enemy individually
• A noise event can chain-investigate: one guard's movement toward a sound may bring them into view of another guard's patrol, creating unintended detection
• Footprints in snow from multiple characters may cross, causing enemies to follow the most recent or most visible trail
• If a body is thrown onto a roof or into a well, it becomes undiscoverable but may also be unreachable for the player to retrieve or hide elsewhere
• Detection buildup pauses or resets when the player enters a concealment spot (bush, building interior) even if still geometrically within the vision cone
• Extinguishing a torch causes the torch-bearer or nearest guard to leave their post to relight it, temporarily removing that vision cone from its patrol area
• In darkness, a character standing in a torch's bright zone is visible at full detection range even if the surrounding area grants reduced visibility
• A civilian fleeing in panic may run toward guards, indirectly drawing attention to the player's general area without triggering an alarm
• Samurai seeing through a disguise bypass the normal detection buildup and attack immediately

10. QA Notes

11. Mechanic Dependencies

• Character Ability System (character abilities emit sound signatures and visual tells (e.g., shuriken flight, pistol flash) that detection processes)
• Stealth Elimination Mechanics (stealth elimination produces noise and visual events that the detection system evaluates for alerting nearby enemies)
• Environmental Interaction System (environmental elements (bushes, snow, darkness, torchlight, water) modify visibility and detection rules)
• Alarm Response System (full detection triggers the alarm response system, which spawns reinforcements and escalates patrol behavior)
• Body Manipulation Mechanics (body hiding prevents corpse discovery, which would otherwise trigger detection and alarm)
• Character Movement System (character movement states (running, crouching, climbing) directly affect detection probability and noise emission)
• Enemy Type Hierarchy (enemy type hierarchy defines different vision cone behaviors, distraction immunity, and detection speeds)
• Civilian Interaction System (civilians possess parallel detection behavior (vision cones, panic on detection) that does not trigger alarms but can compromise stealth)
• Shadow Mode Coordination System (shadow mode allows queuing synchronized actions to exploit brief detection windows and avoid alarm triggers)

12. UI Links

• Difficulty Selection Dialog - The Stealth Detection System is directly affected by the selected difficulty. On Novice, enemies detect players slower; on Professional, enemies detect almost instantly. The difficulty selection dialog configures the detection speed parameter for the entire campaign.
• Post-Mission Results Screen - the Alarm signals statistic reflects how many times the stealth detection system triggered an alarm state; a value of 0 indicates a perfect stealth run
• Enemy Vision Cones - The vision cone is the primary spatial projection of the Stealth Detection System. Cone geometry, angle, length, detection zones, and color states are all driven by detection parameters. The cone's inner/outer zones map directly to detection buildup mechanics.
• Detection Feedback Overlay - The Stealth Detection System produces the enemy sight, suspicion buildup, and alert states that this overlay visualizes through cone color and overhead icons.

References

1. 1.

   Steam Community :: Guide :: Shadow Tactics: Blades of the Shogun 101 (L86-101 of 101) Guards won't immediately see the player at distance; running characters can skim the outer edge of a vision cone and crawl back down before being spotted1: Did not see me Guards won't immediately see you if you're not directly next to them. If you are walking away from them, you can skim on their line of sight while running, and...

2. 2.

   Steam Community :: Guide :: Shadow Tactics: Blades of the Shogun 101 (L34-43 of 101) Raising the alarm spawns extra patrols composed of normal guards (rarely samurai in later missions), creating a graduated consequence for detection1: Lead them Around Guards will react whenever they hear sound - Even when already reacting to something they heard earlier. Yuki can lure them to a spot with her flute,...

3. 3.

   Steam Community :: Guide :: Shadow Tactics: Blades of the Shogun 101 (L74-86 of 101) Guards react to sound events and will leave their post to investigate the noise source before returning to patrol2: Not Agile but not Useless While Takuma cannot melee attack, drag bodies or climb anything other than a ladder, bringing him along with the group is a good idea. He still has 3...

4. 4.

   Steam Community :: Guide :: Shadow Tactics: Blades of the Shogun 101 (L52-63 of 101) Hayato produces no footstep noise while running, allowing him to sprint past patrolling guards undetected3: Spearhead Remember that Mugen has twice as much HP as the other characters. So, if you plan on doing something dangerous that could end up doing damage to someone, try to let...

5. 5.

   Steam Community :: Guide :: Shadow Tactics: Blades of the Shogun 101 (L98-108 of 101) Takuma produces noise when running, making him unsuited for close-range sneaking and highlighting character-specific noise profiles4: First Impressions Count With a bit of preplanning and some dexterity in your fingers you can eliminate guards when they investigate an "accident" and are away from their group....