FS25_UsedPlus - Comprehensive Mod Design & Implementation Guide

Version: 2.7.0 Last Updated: 2026-01-17

Overview
Feature Specifications
- Finance System ✅ IMPLEMENTED
- Credit Score System ✅ IMPLEMENTED
- Search Used System ✅ IMPLEMENTED
- Vehicle Sales System ✅ IMPLEMENTED
- Lease System ✅ IMPLEMENTED
- Land Financing ✅ IMPLEMENTED
- Land Leasing ✅ IMPLEMENTED
- General Loan System ✅ IMPLEMENTED
- Partial Repair & Repaint ✅ IMPLEMENTED
- Trade-In System ✅ IMPLEMENTED
- Finance Manager GUI ✅ IMPLEMENTED
- Financial Dashboard ✅ IMPLEMENTED
- Payment Configuration ✅ IMPLEMENTED
- Vehicle Maintenance System ✅ IMPLEMENTED
- Field Service Kit ✅ IMPLEMENTED
- Vehicle Malfunctions ✅ IMPLEMENTED
- Cross-Mod Compatibility ✅ IMPLEMENTED
- Negotiation System ✅ IMPLEMENTED (v2.6.0)
- Vehicle DNA System ✅ IMPLEMENTED (v2.6.0)
- Used Vehicle Inspection ✅ IMPLEMENTED
Technical Architecture
Implementation Status

Overview

FS25_UsedPlus is a comprehensive financial expansion mod for Farming Simulator 2025 that transforms the built-in vehicle shop into a realistic dealership experience.

Core Systems

System	Description	Status
Finance System	Purchase vehicles/equipment with flexible payment plans (1-15 years)	✅ Complete
Credit Score	FICO-like scoring (300-850) based on financial behavior	✅ Complete
Used Vehicle Search	Agent-based search (Local/Regional/National) for used equipment	✅ Complete
Vehicle Sales	Agent-based selling replaces vanilla instant-sell	✅ Complete
Lease System	Balloon payment leases integrated into Unified Purchase Dialog	✅ Complete
Land Financing	Finance land purchases with lower rates	✅ Complete
Land Leasing	Lease farmland with monthly payments, buyout option	✅ Complete
General Loans	Collateral-based cash loans	✅ Complete
Repair/Repaint	Partial repair with quick buttons and finance option	✅ Complete
Trade-In	Trade existing vehicles toward new purchases	✅ Complete
Finance Manager	ESC menu for managing all financial deals	✅ Complete
Dashboard	Comprehensive financial overview with credit history	✅ Complete
Maintenance	Three-component reliability (engine, electrical, hydraulic)	✅ Complete
Field Service Kit	Multi-mode OBD diagnostic tool for emergency field repairs	✅ Complete
Malfunctions	Realistic breakdowns based on component health	✅ Complete
Payment Config	Per-loan payment customization (skip, min, extra)	✅ Complete
Cross-Mod Compat	Deep integration with RVB, UYT; feature deferral for ELS/HP/BUE	✅ Complete
Negotiation	Counter-offer system with seller personalities and weather effects	✅ Complete
Vehicle DNA	Hidden quality trait (0.0-1.0) affecting long-term reliability	✅ Complete
Inspection	Pre-purchase inspection revealing hidden condition	✅ Complete

Core Philosophy

Realism First - Real-world financial calculations (interest rates, credit scores, depreciation)
Player Choice - Multiple options at every decision point
Risk/Reward - Better deals for better credit, risks in used equipment searches
Integration - Seamless integration with base game shop and finance systems
Replace, Don't Coexist - Replace vanilla systems entirely (like sales) for consistency

Feature Specifications

1. Finance System

Status: ✅ FULLY IMPLEMENTED

Finance any vehicle or equipment with flexible terms.

Key Features

Term range: 1-15 years (credit-gated: 1-5 any, 6-10 Fair+, 11-15 Good+)
Down payment: 0-50%
Interest rates based on credit score and term
Monthly automatic payments via HOUR_CHANGED subscription
Early payoff with prepayment penalty calculation
Full multiplayer support with network events

Technical Implementation

FinanceDeal.lua - Data class with amortization calculations
UnifiedPurchaseDialog.lua - Shop integration dialog (combines Cash/Finance/Lease)
FinanceVehicleEvent.lua - Network event for creating deals
FinancePaymentEvent.lua - Network event for manual payments

Amortized Loan Payment Formula

P = Principal (amount financed)
r = Monthly interest rate (annual rate / 12)
n = Number of months

M = P × [r(1 + r)^n] / [(1 + r)^n - 1]

2. Credit Score System

Status: ✅ FULLY IMPLEMENTED (Enhanced beyond original design)

FICO-like scoring system that affects interest rates and loan availability.

Credit Score Range: 300-850

Rating	Score Range	Interest Adjustment
Excellent	750-850	-1.5%
Good	700-749	-0.5%
Fair	650-699	+0.5%
Poor	600-649	+1.5%
Very Poor	<600	+3.0%

Score Factors

Debt-to-Asset Ratio - Primary factor
Payment History - On-time (+5), Missed (-25), Payoff (+50)
Trend Tracking - Visual indicator (Up/Down/Stable)

Technical Implementation

CreditScore.lua - Score calculation logic
CreditHistory.lua - Historical tracking for trends
Score persists in savegame per farm

3. Search Used System

Status: ✅ FULLY IMPLEMENTED

Agent-based search for used equipment with 3-tier system.

Agent Tiers

Tier	Fee	Time Frame	Success Rate	Discount Range
Local	2% of base	1-2 months	85%	25-40% off
Regional	4% of base	2-4 months	90%	15-30% off
National	6% of base	3-6 months	95%	5-20% off

Minimum Price Threshold

$10,000 minimum item price for Search Used availability
Consumables (seeds, fertilizers) use standard shop flow

Mechanics

TTL (Time To Live) / TTS (Time To Success) countdown
Probabilistic customization matching per configuration option
Depreciation based on generation (age, damage, wear, hours)
Success/failure notifications

Technical Implementation

UsedVehicleSearch.lua - Search data class
UsedVehicleManager.lua - Queue processing
UsedSearchDialog.lua - Tier selection dialog
RequestUsedItemEvent.lua / UsedItemFoundEvent.lua - Network events

4. Vehicle Sales System

Status: ✅ FULLY IMPLEMENTED

Replaces vanilla instant-sell with agent-based marketplace.

Agent Tiers (Selling)

Tier	Fee	Time Frame	Success Rate	Return Range
Local	$50	1-2 months	85%	60-75%
Regional	$200	2-4 months	90%	75-90%
National	$500	3-6 months	95%	90-100%

Value Hierarchy

Trade-In (50-65%, instant) - Lowest return, fastest
Local Agent (60-75%, 1-2 months)
Regional Agent (75-90%, 2-4 months)
National Agent (90-100%, 3-6 months) - Highest return, slowest

Technical Implementation

VehicleSaleListing.lua - Sale listing data class
VehicleSaleManager.lua - Listing management
SellVehicleDialog.lua - Agent selection
SaleOfferDialog.lua - Accept/decline offers
InGameMenuVehiclesFrameExtension.lua - Hook sell button

5. Lease System

Status: ✅ FULLY IMPLEMENTED (Integrated into Unified Purchase Dialog)

Implementation Approach

Leasing is integrated into the Unified Purchase Dialog alongside Cash and Finance options, rather than replacing the game's lease system separately.

Features

Custom lease terms (1-5 years)
Lower down payment max (20% vs 50% for finance)
Residual value (balloon payment) calculation
Vehicle marked as "LEASED" - cannot sell
Damage penalties at lease end
Early termination with fee
Credit score affects lease rates

Lease Payment Formula (Balloon)

P = Price - Down Payment
FV = Residual Value (balloon)
r = Monthly interest rate
n = Term in months

M = (P - FV/(1+r)^n) * [r(1+r)^n] / [(1+r)^n - 1]

Residual Value by Term

Term	Residual
1-2 years	65%
3 years	55%
4 years	45%
5 years	35%

Technical Implementation

LeaseDeal.lua - Data class with balloon calculations
UnifiedPurchaseDialog.lua - Combined Cash/Finance/Lease dialog
LeaseVehicleEvent.lua - Network event
TerminateLeaseEvent.lua - Early termination

6. Land Financing

Status: ✅ FULLY IMPLEMENTED

Finance farmland purchases with lower interest rates.

Features

Lower base rate (3.5% vs 4.5% for vehicles)
Longer terms available (up to 30 years)
Down payment: 0-40%
Land ownership transfers immediately
3 missed payments = land seizure + credit damage

Technical Implementation

UnifiedLandPurchaseDialog.lua - Combined Cash/Finance/Lease dialog
FarmlandManagerExtension.lua - Hook land purchase

7. Land Leasing

Status: ✅ FULLY IMPLEMENTED

Lease farmland instead of purchasing outright.

Features

Lease land for 1, 3, 5, or 10-year terms
Shorter terms have higher markup rates (20% for 1 year, 5% for 10 years)
Monthly lease payments automatically deducted
Expiration warnings at 3 months, 1 month, and 1 week before end
Land reverts to NPC ownership upon lease expiration
Lease renewal option available before expiration
Option to buy out lease (convert to purchase) with discount

Lease Terms

Term	Markup Rate	Buyout Discount
1 year	20%	0%
3 years	12%	5%
5 years	8%	10%
10 years	5%	15%

Technical Implementation

LandLeaseDialog.lua - Lease configuration dialog
UnifiedLandPurchaseDialog.lua - Combined Cash/Finance/Lease selection
InGameMenuMapFrameExtension.lua - Map context menu integration

8. General Loan System

Status: ✅ FULLY IMPLEMENTED

Collateral-based cash loans against farm assets.

Features

Access from Finance Manager > "Take Loan" button
Collateral: 50% of vehicle value + 60% of land value
Credit score affects max loan and interest rate
Dropdown selection for amount (% of max) and term
Real-time payment preview
Annuity-based repayment

Technical Implementation

TakeLoanDialog.lua - Loan configuration
TakeLoanEvent.lua - Network event
Uses FinanceDeal with dealType = 3 (loan)

9. Partial Repair & Repaint System

Status: ✅ FULLY IMPLEMENTED

Replace game's repair dialog with custom partial repair.

Features

Quick percentage buttons: 25%, 50%, 75%, 100%
Separate dialogs for repair and repaint
Real-time cost calculation
Option to finance repair costs
Works at all dealers/workshops
v2.7.0: Workshop charges extra for fuel leak (+2% vehicle price) and flat tire (+1% vehicle price) repairs

Technical Implementation

RepairDialog.lua - Repair configuration
RepairFinanceDialog.lua - Finance repair option
RepairVehicleEvent.lua - Network event
VehicleSellingPointExtension.lua - Workshop hook

10. Trade-In System

Status: ✅ FULLY IMPLEMENTED

Trade existing vehicles toward new purchases.

Features

Trade-in value: 50-65% of vanilla sell price
5% bonus for same-brand purchases
Condition affects value (damage/wear multipliers)
Shows vehicle condition before trade
Only non-financed, owned vehicles eligible

Value Calculation

Base = Vanilla Sell Price × 0.50 to 0.65
Brand Bonus = +5% if same brand
Condition = × (1 - damage × 0.3) × (1 - wear × 0.2)
Final = Base × Brand Bonus × Condition

Technical Implementation

TradeInDialog.lua - Vehicle selection
TradeInCalculations.lua - Value calculation

11. Finance Manager GUI

Status: ✅ FULLY IMPLEMENTED

ESC menu for managing all financial operations.

Features

Overview of all active deals (finance, lease, loan)
Summary statistics (total debt, monthly obligations)
Detail view with payment options
Quick buttons: 1 month, 6 months, 1 year, payoff
Active sale listings section
Take Loan button
Hotkey: Shift+F

Technical Implementation

FinanceManagerFrame.lua - Main screen
FinanceDetailFrame.lua - Payment screen
InGameMenuMapFrameExtension.lua - ESC menu integration

12. Financial Dashboard

Status: ✅ FULLY IMPLEMENTED

Comprehensive financial overview.

Features

Credit score with trend indicator
Credit history timeline
Debt-to-asset ratio meter
Monthly obligations breakdown by type
Upcoming payments list

Technical Implementation

FinancialDashboard.lua - Dashboard screen

13. Payment Configuration System

Status: ✅ FULLY IMPLEMENTED

Allow players to customize payment amounts per loan.

Payment Options

Payment Type	Description	Credit Impact
Skip	No payment, balance grows (negative amortization)	-25
Minimum	Interest-only payment, balance unchanged	0
Standard	Original amortized payment	+5
1.5x Extra	50% extra reduces principal faster	+5
2x Extra	Double payment for aggressive payoff	+5
Custom	Player-specified amount	Varies

Minimum Payment Formula

Minimum = Current Balance × (Annual Rate / 12)

This is the interest-only amount. Paying only this keeps balance unchanged but avoids default.

Technical Implementation

Payment multiplier stored in FinanceDeal.paymentMultiplier
SetPaymentConfigEvent.lua - Multiplayer sync
Accessed via Finance Manager → Deal Details → Configure Payment button

14. Vehicle Maintenance System

Status: ✅ FULLY IMPLEMENTED

Comprehensive reliability and maintenance system for vehicles.

Three-Component Reliability

Engine Health: Affects power output, fuel efficiency, and starting reliability
Electrical Health: Impacts lights, gauges, and electronic systems
Hydraulic Health: Controls implement lift, steering assist, and attachments

Fluid Systems

Engine Oil: Depletes with use, low oil causes engine damage
Hydraulic Fluid: Powers implements and steering
Fuel: Fuel leaks drain tank over time when detected

Tire System

Three tire quality tiers: Retread, Normal, Quality
Tire tread wears over time based on usage and terrain
Worn tires reduce traction and increase slip
Flat tires cause steering pull and reduce max speed

Technical Implementation

UsedPlusMaintenance.lua - Vehicle specialization
MaintenanceReportDialog.lua - Owned vehicle maintenance view
FluidsDialog.lua - Fluid service interface
TiresDialog.lua - Tire service interface

15. Field Service Kit

Status: ✅ FULLY IMPLEMENTED (v2.8.0 Balanced)

Portable emergency repair system with OBD diagnostic capabilities. Designed as a tactical tool for field emergencies, not a replacement for workshop repair.

Kit Tiers

Tier	Price	Reliability Multiplier	Diagnosis Accuracy
Basic	$5,000	1.0x	Standard readings
Professional	$12,000	1.25x	Enhanced readings
Master	$25,000	1.5x	Complete diagnostics

OBD Scanner Modes (v2.7.0)

Mode	Function
Diagnose Component	Diagnostic minigame for engine/electrical/hydraulic (ONE-TIME per system)
Locate Malfunctions	Quick view of all active malfunctions
Tire Service	Per-wheel inspection and repair options
RVB System Analysis	Detailed RVB part inspection (only visible when RVB installed)

Reliability Restoration Limits (v2.8.0)

The OBD Scanner is field repair equipment with intentional limitations to prevent exploit:

Constraint	Limit	Rationale
One-Time Diagnosis	Each system (engine, electrical, hydraulic) can only receive ONE diagnostic boost per vehicle	Prevents spam-buying kits for unlimited restoration
Field Repair Cap	Maximum 80% reliability	Field repairs can't match workshop quality
Vehicle Ceiling	Respects `maxReliabilityCeiling`	Aging equipment has permanent degradation
Effective Cap	`min(80%, vehicleCeiling)`	Uses whichever is lower

Seizure repair is separate - fixing a seized component does NOT consume the diagnostic boost (it's emergency repair for a critical failure).

Diagnosis Boost Amounts

Outcome	Base Boost	With Master Kit (1.5x)
Perfect (right system + right diagnosis)	8-15%	12-22.5%
Good (right system + wrong diagnosis)	4-8%	6-12%
Poor (wrong system)	1-3%	1.5-4.5%

All boosts capped at 25% maximum per diagnosis.

Example Scenarios

New Tractor (vehicle ceiling: 100%)
├── Engine reliability: 45%
├── OBD diagnoses engine (perfect) → +15% = 60% (capped at 80%)
├── Try to diagnose engine again → "Already diagnosed - OBD boost exhausted"
├── Engine seizes later → OBD CAN fix seizure (separate mechanic)
└── Want reliability above 80%? → Shop repair required

Old Tractor (vehicle ceiling: 65% due to age/wear)
├── Engine reliability: 40%
├── OBD diagnoses engine (perfect) → +15% = 55% (capped at 65%)
├── Even perfect diagnosis can't exceed 65%
└── Vehicle needs replacement eventually

Gameplay Flow

Player buys Field Service Kit from shop
Player carries kit to vehicle (it's a hand tool)
Player activates kit - OBD scanner dialog opens
Mode Selection: Choose diagnostic mode
Diagnose Component:
- System Selection: Engine, Electrical, or Hydraulic
- If already diagnosed: Shows "boost exhausted" warning
- OBD Diagnostic Reading: 3 codes/readings displayed
- Diagnosis Choice: Pick from 4 possible diagnoses
- Outcome: Correct diagnosis = better repair (up to 80% cap)
Kit is consumed regardless of outcome (single use)

Technical Implementation

DiagnosisData.lua - Scenario definitions, outcome calculations
FieldServiceKit.lua - Vehicle specialization (hand tool)
FieldServiceKitDialog.lua - Multi-step diagnostic dialog with mode selection, one-time tracking
fieldServiceKit.xml - Store item definition
UsedPlusMaintenance.lua - Tracks obdDiagnosesUsed per vehicle (persisted)

16. Vehicle Malfunctions

Status: ✅ FULLY IMPLEMENTED

Realistic breakdown events based on component health.

Hydraulic Malfunctions (Signature Feature)

Malfunction	Trigger	Effect
Runaway Engine	Oil AND hydraulic <10%	Speed 150%, brakes 40%
Implement Stuck	Hydraulic <25%	Can't raise/lower
Hydraulic Surge	Hydraulic <60%	Sudden steering pull
Implement Drag	Hydraulic <35%	Max speed 60%

Engine Malfunctions

Overheating: Engine temperature rises, power reduces, eventual stall
Misfiring: Random power fluctuations and rough running
Stalling: Engine cuts out unexpectedly, restart required
Hard Starting: Difficulty starting in cold conditions with worn engine

Electrical Malfunctions

Electrical Cutout: Temporary loss of electrical systems
Gauge Failures: Instrument readings become unreliable
Light Flickering: Headlights and work lights flicker or fail

Tire Malfunctions

Flat Tire: Sudden tire failure causing steering pull
Slow Leak: Gradual pressure loss over time

Fuel System Malfunctions

Fuel Leak: Tank slowly drains fuel when parked or running

17. Cross-Mod Compatibility System

Status: ✅ FULLY IMPLEMENTED (Deep Integration)

Intelligent integration with popular vehicle maintenance and financial mods.

Deeply Integrated Mods

Mod	Integration Type	Details
Real Vehicle Breakdowns	Full Integration	DNA affects part lifetimes, workshop injection, OBD display
Use Up Your Tyres	Full Integration	Two-way sync, quality/DNA wear multipliers, per-wheel display
EnhancedLoanSystem	Deep Integration	Loans display in Finance Manager, Pay Early works
HirePurchasing	Deep Integration	Leases display in Finance Manager
Employment	Deep Integration	Worker wages in monthly obligations

Feature Deferral

BuyUsedEquipment - UsedPlus hides Search button, BUE handles used search
AdvancedMaintenance - NOT RECOMMENDED (conflicts with UsedPlus maintenance)

See COMPATIBILITY.md for detailed technical analysis.

18. Negotiation System

Status: ✅ FULLY IMPLEMENTED (v2.6.0)

Counter-offer system for used vehicle purchases with seller personalities.

Seller Personalities (DNA-Driven)

Personality	DNA Range	Minimum Acceptance	Behavior
Desperate	0.00-0.29 (Lemons)	75%	Eager to sell, accepts low offers
Motivated	0.30-0.49	80%	Room to negotiate
Reasonable	0.50-0.69	85%	Standard negotiation
Firm	0.70-0.79	92%	Don't lowball
Immovable	0.80-1.00 (Workhorses)	98%	Know what they have

Walk-Away Risk

Gap Below Threshold	Risk Level	Result
Within 5%	Safe	Always counter
5-10% below	Low	Usually counter
10-15% below	Medium	50/50
15-20% below	High	Usually reject
>20% below	Insulted	Permanent walk-away

Mechanic's Whisper

Before offering, mechanic hints at seller psychology:

"They seem pretty eager to sell..." = Desperate (go low)
"Seems like a reasonable person" = Reasonable
"This seller knows exactly what they have" = Immovable (don't lowball)

Weather Effects

Storms make sellers anxious:

Hail: +12% acceptance bonus
Storm: +8% acceptance bonus
Rain/Snow: +5% acceptance bonus

Technical Implementation

NegotiationDialog.lua - Counter-offer interface
NegotiationCalculations.lua - Personality/weather effects
DNA stored on listing, determines personality at search completion

19. Vehicle DNA System

Status: ✅ FULLY IMPLEMENTED (v2.6.0)

Hidden quality trait affecting long-term vehicle reliability.

DNA Ranges

DNA Range	Classification	Long-Term Effect
0.00-0.29	Lemon	Repairs make it worse. Death spiral.
0.30-0.69	Average	Normal degradation
0.70-0.89	Workhorse	Minimal degradation
0.90-1.00	Legendary	IMMUNE to repair degradation

DNA Effects

Repair Degradation - Each repair slightly reduces max reliability (except Legendary)
Tire Wear - Lemons 1.4x faster, Workhorses 0.6x slower (with UYT)
RVB Part Wear - DNA affects RVB part lifetime multipliers
Seller Personality - DNA determines seller behavior in negotiations

Mechanic Inspection Hints

"I'd burn some sage before driving this one..." = Lemon
"About what you'd expect from the factory" = Average
"In 30 years, I've seen maybe a dozen this well built" = Legendary

Technical Implementation

DNA assigned at vehicle spawn (new) or search completion (used)
Stored in spec_usedPlusMaintenance.vehicleDNA
Persists through save/load

20. Used Vehicle Inspection System

Status: ✅ FULLY IMPLEMENTED

Pre-purchase inspection revealing hidden vehicle condition.

Inspection Features

Visible Stats - Age, hours, damage, wear (shown in preview)
Hidden Stats - Reliability, DNA hints (revealed by inspection)
RVB Part Data - Component status if RVB installed
UYT Tire Data - Per-wheel condition if UYT installed

Inspection Flow

Agent finds used vehicle → UsedVehiclePreviewDialog opens
Player sees visible stats and "Not Inspected" warning
Player can "Buy As-Is" (risk) or "Request Inspection"
Inspection fee paid (based on vehicle value)
InspectionReportDialog shows full vehicle condition
Player makes informed purchase decision

Inspection Report Contents

Overall Reliability Score
Engine/Electrical/Hydraulic health
DNA classification hint (mechanic quote)
RVB component status (if installed)
Per-wheel tire condition (if UYT installed)
Estimated repair costs

Technical Implementation

UsedVehiclePreviewDialog.lua - Initial preview with visible stats
InspectionReportDialog.lua - Full inspection results
Pre-generated RVB/UYT data stored on listing

Technical Architecture

File Structure

FS25_UsedPlus/
├── modDesc.xml
├── icon.dds
├── gui/                          # XML dialog definitions
├── src/
│   ├── main.lua                  # Entry point
│   ├── data/                     # Data classes
│   │   ├── CreditHistory.lua
│   │   ├── CreditScore.lua
│   │   ├── FinanceDeal.lua
│   │   ├── LeaseDeal.lua
│   │   ├── UsedVehicleSearch.lua
│   │   └── VehicleSaleListing.lua
│   ├── utils/                    # Calculations
│   │   ├── FinanceCalculations.lua
│   │   ├── DepreciationCalculations.lua
│   │   ├── ConfigurationDetector.lua
│   │   ├── TradeInCalculations.lua
│   │   ├── NegotiationCalculations.lua
│   │   └── ModCompatibility.lua
│   ├── events/                   # Network events (14+ total)
│   ├── managers/
│   │   ├── FinanceManager.lua
│   │   ├── UsedVehicleManager.lua
│   │   └── VehicleSaleManager.lua
│   ├── specializations/
│   │   ├── UsedPlusMaintenance.lua
│   │   └── FieldServiceKit.lua
│   ├── gui/                      # Dialog controllers (15+ total)
│   └── extensions/               # Game hooks (10+ total)
└── translations/

Key Patterns Used

MessageDialog - All dialogs extend MessageDialog
Event Pattern - Event.sendToServer() for multiplayer
Manager Pattern - Singletons with HOUR_CHANGED subscription
Extension Pattern - Utils.appendedFunction / Utils.overwrittenFunction
TTL/TTS Queue - Async operations for searches and sales
DNA System - Hidden quality affecting multiple subsystems

Implementation Status

Fully Implemented ✅

Finance System
Credit Score System (enhanced)
Used Vehicle Search
Vehicle Sales System
Lease System (integrated into Unified Purchase Dialog)
General Loan System
Partial Repair & Repaint
Trade-In System
Finance Manager GUI
Financial Dashboard
Payment Configuration System
Land Financing
Land Leasing
Vehicle Maintenance System
Vehicle Malfunctions
Field Service Kit (with multi-mode v2.7.0)
Cross-Mod Compatibility (RVB, UYT, ELS, HP, Employment)
Negotiation System with Seller Personalities
Vehicle DNA System
Used Vehicle Inspection System

In Progress 🔄

Delayed Inspection System (v2.7.0) - Time-delayed inspection where player pays, waits game hours, receives notification when ready

Future Considerations 📋

Inspection Tiers - Quick/Standard/Comprehensive with different costs, times, and data revealed
Seasonal Pricing - Equipment prices fluctuate by season
Auction System - Competitive bidding on rare equipment

Document History

2026-01-17 (for v2.7.0) - Comprehensive Status Update

Updated all feature statuses to reflect current implementation
Added Section 18: Negotiation System
Added Section 19: Vehicle DNA System
Added Section 20: Used Vehicle Inspection System
Updated Field Service Kit with multi-mode
Updated Lease System status to IMPLEMENTED
Updated Payment Configuration status to IMPLEMENTED
Added delayed inspection to "In Progress"
Updated technical architecture

2025-12-28 (for v2.5.0) - Documentation Sync

Updated Land Leasing status
Added Vehicle Maintenance and Malfunctions sections

2025-11-27 (for v1.8.0) - Design Document Update

Added Payment Configuration System design
Added implemented features not in original design
Updated lease system approach
Marked implementation status

2025-11-21 - Original Comprehensive Design

Initial comprehensive design document

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FS25_UsedPlus - Comprehensive Mod Design & Implementation Guide

Table of Contents

Overview

Core Systems

Core Philosophy

Feature Specifications

1. Finance System

Key Features

Technical Implementation

Amortized Loan Payment Formula

2. Credit Score System

Credit Score Range: 300-850

Score Factors

Technical Implementation

3. Search Used System

Agent Tiers

Minimum Price Threshold

Mechanics

Technical Implementation

4. Vehicle Sales System

Agent Tiers (Selling)

Value Hierarchy

Technical Implementation

5. Lease System

Implementation Approach

Features

Lease Payment Formula (Balloon)

Residual Value by Term

Technical Implementation

6. Land Financing

Features

Technical Implementation

7. Land Leasing

Features

Lease Terms

Technical Implementation

8. General Loan System

Features

Technical Implementation

9. Partial Repair & Repaint System

Features

Technical Implementation

10. Trade-In System

Features

Value Calculation

Technical Implementation

11. Finance Manager GUI

Features

Technical Implementation

12. Financial Dashboard

Features

Technical Implementation

13. Payment Configuration System

Payment Options

Minimum Payment Formula

Technical Implementation

14. Vehicle Maintenance System

Three-Component Reliability

Fluid Systems

Tire System

Technical Implementation

15. Field Service Kit

Kit Tiers

OBD Scanner Modes (v2.7.0)

Reliability Restoration Limits (v2.8.0)

Diagnosis Boost Amounts

Example Scenarios

Gameplay Flow

Technical Implementation

16. Vehicle Malfunctions

Hydraulic Malfunctions (Signature Feature)

Engine Malfunctions

Electrical Malfunctions