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Why are my X and Y coordinates showing NaN in Scratch turbo mode?

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💡 Struggling with mysterious NaN values in your Scratch project? Variables acting weird? 🚀 Get Debug Help

CD

CodeDebugger_2025

Posted on July 26, 2025 • Intermediate

🐛 Strange NaN values appearing in turbo mode

Hey everyone! I’m working on an AI project and running into a weird issue. When I enable turbo mode, my X and Y coordinate variables start showing “NaN” instead of numbers. This is really frustrating because:

  • The project works fine in normal speed
  • Only happens when turbo mode is enabled
  • Breaks all my movement and collision detection
  • Can’t figure out what’s causing the calculation to fail

Has anyone encountered this before? I really need to get this working in turbo mode for testing. Any help would be amazing! 🙏

DS

DebugSpecialist_Pro

Replied 3 hours later • ⭐ Best Answer

Great question @CodeDebugger_2025! NaN (Not a Number) values are a common issue in Scratch, especially in turbo mode. Here’s a comprehensive guide to identify and fix this problem:

🔍 Understanding NaN in Scratch

NaN occurs when mathematical operations produce undefined results. Here’s the debugging process:

flowchart TD A[🎮 Project Running] --> B{Turbo Mode Enabled?} B -->|No| C[Normal Execution] B -->|Yes| D[Faster Loop Execution] D --> E{Division by Zero?} E -->|Yes| F[🚨 NaN Generated] E -->|No| G{Square Root of Negative?} G -->|Yes| F G -->|No| H{Invalid Math Operation?} H -->|Yes| F H -->|No| I[✅ Normal Values] F --> J[Variables Show NaN] J --> K[🐛 Project Breaks] C --> L[Slower Execution] L --> M[Race Conditions Less Likely] M --> N[✅ Project Works] style F fill:#ffebee style K fill:#ffebee style I fill:#e8f5e8 style N fill:#e8f5e8

🔧 Common Causes and Solutions

1. Division by Zero

The most common cause of NaN in Scratch:

    // ❌ PROBLEMATIC CODE
when flag clicked
forever
set [speed v] to ((distance to [Player v]) / (timer))
// If timer is 0, this creates NaN!
end
  
    // ✅ FIXED VERSION
when flag clicked
forever
if <(timer) > [0]> then
set [speed v] to ((distance to [Player v]) / (timer))
else
set [speed v] to [0]
end
end
2. Square Root of Negative Numbers

Another common source of NaN:

    // ❌ PROBLEMATIC CODE
set [distance v] to (sqrt of ((x position) - (target x)))
// If (x position) < (target x), this creates NaN!
  
    // ✅ FIXED VERSION
set [dx v] to ((x position) - (target x))
set [distance v] to (sqrt of (([abs v] of (dx)) * ([abs v] of (dx))))
3. Race Conditions in Turbo Mode

Variables updating too fast can cause calculation errors:

    // ❌ PROBLEMATIC CODE
when flag clicked
forever
change [x v] by (velocity)
set [velocity v] to ((target x) - (x))
// In turbo mode, this can create feedback loops!
end
  
    // ✅ FIXED VERSION
when flag clicked
forever
set [old x v] to (x)
change [x v] by (velocity)
if <not <(old x) = (x)>> then
set [velocity v] to ((target x) - (x))
end
wait [0.01] seconds // Small delay prevents race conditions
end

🛠️ Debugging Techniques

1. Add Debug Displays
    when flag clicked
forever
say (join [X: ] (join (x position) (join [ Y: ] (y position)))) for [0.1] seconds
// This helps you see when NaN appears
end
2. Variable Validation
    define Check Variable [value]
if <(value) = (value)> then
// Value is valid (NaN ≠ NaN in most systems)
set [is valid v] to [true]
else
set [is valid v] to [false]
set [value v] to [0] // Reset to safe value
end
3. Safe Math Operations
    define Safe Divide [numerator] [denominator]
if <(denominator) = [0]> then
set [result v] to [0]
else
set [result v] to ((numerator) / (denominator))
end

🚀 Advanced Prevention Strategies

1. Input Validation System
    define Validate Coordinates
if <not <(x position) = (x position)>> then
go to x: [0] y: (y position)
end
if <not <(y position) = (y position)>> then
go to x: (x position) y: [0]
end
2. Turbo Mode Safe Loops
    when flag clicked
forever
// Your main logic here

// Add small delay for turbo mode stability
if <(turbo mode) = [true]> then
wait [0.001] seconds
end
end
3. Error Recovery System
    define Reset If NaN
if <not <(player x) = (player x)>> then
set [player x v] to [0]
broadcast [Position Reset v]
end
if <not <(player y) = (player y)>> then
set [player y v] to [0]
broadcast [Position Reset v]
end

🎯 Specific Fixes for AI Projects

  • Pathfinding: Always check if target coordinates are valid before calculating paths
  • Distance Calculations: Use absolute values to prevent negative square roots
  • Velocity Updates: Limit velocity changes per frame to prevent oscillation
  • Collision Detection: Validate sprite positions before collision checks

🔍 Quick Diagnostic Checklist

  1. Check for division by zero in all calculations
  2. Verify no square roots of negative numbers
  3. Look for rapid variable updates in loops
  4. Test with and without turbo mode
  5. Add debug output to track when NaN first appears
  6. Use “wait” blocks to slow down critical calculations

Following these strategies should eliminate NaN issues and make your project stable in both normal and turbo modes!

VB

Vibelf_Community

Pinned Message • Moderator

🔧 Need Advanced Debugging Help?

Excellent troubleshooting discussion! For developers dealing with complex debugging scenarios, our expert tutors can help with:

  • 🐛 Advanced error detection and handling
  • ⚡ Performance optimization for turbo mode
  • 🧮 Complex mathematical operations in Scratch
  • 🤖 AI behavior debugging and optimization

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