Shop Combat & Karma System

Status: Designed Author: Nathan + Claude Last Updated: 2026-04-07 Implements Pillar: Risk/reward decisions, moral choice, replayability

Overview

Players can choose to rob the merchant at any shop node instead of buying. This triggers a unique combat encounter against the Merchant (and bodyguards at higher karma debt). Winning gives all shop items for free. Losing ends the run. A persistent karma system tracks robberies across runs, escalating consequences: higher prices, bodyguards, locked items, and altered narrative. Redemption is possible through legitimate purchases and shrine atonement.

The system adds a high-stakes moral dimension to every shop visit — do you play fair and invest gold, or risk everything for free loot?

Player Fantasy

The temptation of the shortcut. Every shop visit becomes a tense decision: "I could just take it all." The player who robs feels the thrill of getting away with it — but the creeping dread of consequences. The player who resists feels virtuous, but always wonders "what if?" The player deep in karma debt feels hunted — the merchant remembers, and the world pushes back.

Reference: Undertale's genocide route (consequences persist), Slay the Spire's risk/reward node choices, Balatro's "do I push my luck" tension.

Detailed Design

Core Flow

At any shop node, the player sees three options:

1. Buy — normal shop behavior (browse, purchase with gold)
2. Rob — initiate combat against the Merchant
3. Leave — exit shop, proceed to next floor (no purchase, no fight)

Robbery Combat

When the player clicks "Rob":

1. Warning dialog: "The Merchant won't go quietly. Are you sure?" with karma indicator
2. If confirmed, transition to combat scene with the Merchant (+ bodyguards based on karma)
3. Win: all shop items (relics, consumables, heal) added to player inventory
   • Relics respect the 8-relic cap — if full, swap picker shown
   • Consumables respect slot limit — excess discarded
   • Heal option auto-applied
   • Karma decreases by 10
4. Lose: run ends (game over flow, skill points still awarded)
5. During combat, player can Flee (replaces "Score" button on turn 1 only)
   • Flee = leave shop with nothing, no karma change, merchant remembers (dialogue only)

The Merchant (Enemy)

Unique enemy not in the normal pool. The Merchant is a defensive fighter — shields up, dirty tricks, calls for help.

Merchant Interference Actions (unique to this enemy):

Merchant Passive — "Coin Purse": Immune to Burn (can't set a merchant on fire — bad for business). First 3 damage per hit absorbed (like Thick Hide but weaker).

Merchant Sprite: Hooded figure, uses existing shop_bg merchant silhouette style.

Bodyguards (Karma-Scaled)

At higher karma debt, the Merchant hires protection:

Bodyguards use existing enemy sprites (pick from basic/elite pool) with "Hired" prefix in display name.

Karma System

Persistence: Stored in user://karma.save, independent of run data (survives across runs like skill tree).

Karma Value: Integer, starts at 0. Negative = criminal, positive = virtuous.

Karma Consequences (applied at shop generation):

Redemption: Karma naturally drifts toward 0 through legitimate play. A player at -30 karma needs ~30 purchases or 2 shrine atonements to return to neutral. This takes 5-8 runs of honest shopping.

Shrine Atonement

When karma < -5, shrines gain an additional blessing option:

• "Atonement": Pay 50 gold. Karma +15. Flavor text: "The shrine absolves a fraction of your sins."
• Appears alongside normal shrine blessings (heal, reroll, consumable)
• Only available when karma is negative

Narrative Integration

Merchant Dialogue changes based on karma (shown as flavor text at top of shop screen):

First Robbery Cutscene (plays once via CutsceneManager):

• "The merchant's eyes widen as you reach for your dice. This isn't a negotiation."
• After victory: "You gather the merchant's wares. Somewhere, a ledger records your debt."

Karma Warning on Game Over/Victory:

• If karma < -10, defeat screen shows: "The merchant's guild will remember this."
• If karma < -20, victory screen shows: "Your reputation precedes you. Merchants whisper your name."

States and Transitions

SHOP_ENTER
  |-- Player browses items --> SHOPPING (normal flow)
  |-- Player clicks "Rob" --> ROBBERY_WARNING
  |-- Player clicks "Leave" --> MAP (no purchase)
  
ROBBERY_WARNING
  |-- Player confirms --> ROBBERY_COMBAT
  |-- Player cancels --> SHOPPING
  
ROBBERY_COMBAT
  |-- Player wins --> LOOT_ALL (items added, karma -10)
  |-- Player loses --> GAME_OVER
  |-- Player flees (turn 1 only) --> MAP (nothing gained, dialogue noted)
  
LOOT_ALL
  |-- Relic cap check --> SWAP_PICKER (if at cap) or MAP

Interactions with Other Systems

Formulas

Merchant HP Scaling

merchant_hp = BASE_MERCHANT_HP[act] + abs(karma) * 2

Where BASE_MERCHANT_HP = {1: 80, 2: 120, 3: 160}.

At -30 karma, Act 3 merchant has 160 + 60 = 220 HP (approaching boss territory).

Price Modifier

karma_price_mult = 1.0 + max(0, abs(min(karma, 0))) * 0.025

At karma 0: 1.0x. At -10: 1.25x. At -20: 1.5x. At -30: 1.75x.

Capped at 2.0x (karma -40 or lower).

Merchant Shield Per Turn

shield_per_turn = BASE_SHIELD[act] + max(0, abs(min(karma, 0)) / 10) * 4

At karma -30, Act 1: 8 + 12 = 20 shield/turn.

Loot Value

total_loot_value = sum(item_prices_in_shop)

Typically 200-500g worth of items per shop. This is the risk/reward calculation: spend 0g for ~300g worth of items, but risk game over + karma debt.

Karma Decay (Natural Drift)

Karma does NOT auto-decay. It only changes through player actions (buy, rob, atone). This means consequences are permanent until actively redeemed.

Edge Cases

Dependencies

Tuning Knobs

Visual/Audio Requirements

Visual:

• Merchant sprite: hooded figure with coin purse (1-bit style, existing art direction)
• Thug sprite: reuse basic enemy sprite with dark tint
• Enforcer sprite: reuse elite enemy sprite with gold tint
• "Rob" button: red text, danger styling, positioned below "Leave" button
• Karma indicator: small icon near gold display on shop screen (skull for negative, star for positive)
• Price markup: original price shown with strikethrough, karma-inflated price in red

Audio:

• Robbery initiation: tense SFX (reuse enemy_snipe or new "confrontation" sound)
• Merchant defeat: coin shower SFX (reuse coin sounds from shop purchase)
• Karma warning: low rumble on shop enter when karma < -10
• Atonement: shrine chime + ascending tone

UI Requirements

Shop Screen Changes:

• "Rob" button: bottom of shop UI, red text, small (doesn't dominate the layout)
• Karma indicator: top-right corner, shows skull icon + number when negative
• Price display: when karma < 0, show base price crossed out + inflated price
• Locked items: greyed out with "[LOCKED]" label and padlock icon
• Merchant dialogue: flavor text banner at top of shop, changes with karma

Combat Screen Changes:

• Merchant name displays as "The Merchant" (not a generic enemy name)
• "Flee" button replaces "Score" on turn 1 of robbery combat only
• Bodyguard names: "Hired Thug", "Hired Enforcer"

Confirmation Dialog:

• "Rob the Merchant?" + karma display + bodyguard warning
• "This will anger the Merchant's Guild." (if karma already negative)
• Confirm / Cancel buttons

Acceptance Criteria

1. Player can click "Rob" at any shop to initiate combat with the Merchant
2. Winning robbery grants all shop items (respecting caps, with swap picker)
3. Losing robbery triggers normal game over flow
4. Flee option available on turn 1 only, returns to map with no loot
5. Karma persists across runs in user://karma.save
6. Karma decreases by 10 on successful robbery
7. Karma increases by 1 per purchase, +15 per shrine atonement
8. Shop prices scale with negative karma (verified at -10, -20, -30)
9. Bodyguards appear at correct karma thresholds
10. Merchant HP scales with act + karma level
11. Merchant uses unique interference actions (POCKET_SAND, STEAL_GOLD, etc.)
12. Shrine shows Atonement option when karma < -5
13. Merchant dialogue changes with karma level
14. Locked items appear at karma -20 and below (heal always available)
15. Loyal Customer discount appears at karma +10
16. Merchant Prince keystone stacks correctly with karma price modifier
17. Wanderer relic guarantee applies to robbery loot
18. Two robberies in one run (F4 + F9) both apply karma and bodyguard escalation
19. First robbery cutscene plays once via CutsceneManager

New Achievements

Open Questions

1. Should karma affect non-shop systems? IMPLEMENTED — karma now affects:
   • Guardian choices (Kill/Save dialogue, resistance)
   • Shop prices (existing)
   • Multiple endings (determines Good/Bad/True ending)
   • Memory fragment collection (karma gates truth)
2. Should there be a "Pacifist" achievement? Win without ever robbing (karma >= 0 after 10+ runs)
3. How does this interact with the Player-Echo Boss? Could the echo boss inherit karma state — a "good" echo boss is weaker but the merchant helps you, an "evil" echo boss is stronger
4. Multiplayer expansion: If co-op is ever added, does one player's robbery affect the other's karma?
5. Visual karma indicator in hub? A wanted poster that appears on the camp wall when karma < -10