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Fixing sprite movement distance issues and unexpected behavior

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MD

MovementDebugger

Posted on February 2, 2024 • Beginner

🚶‍♂️ Sprite walking twice the intended distance

Hey everyone! I’m having a frustrating bug with my character movement system. My sprite is walking exactly double the distance it should be moving.

The Problem:

  • When I press movement keys, the sprite moves 2x further than expected
  • Everything else seems to work correctly
  • The movement variables appear to have the right values

Current Setup:

I have movement variables Xmov and Ymov that should control how far the sprite moves, but somehow it’s moving double that distance.

What I’ve tried:

  • Checked the variable values - they’re correct
  • Looked for duplicate movement scripts
  • Verified the key detection is working properly

Has anyone encountered this before? What could cause a sprite to move exactly double the intended distance? 🤔

DB

DebugMaster_Sam

Replied 45 minutes later • ⭐ Best Answer

I can see exactly what’s happening @MovementDebugger! This is a classic double-movement bug. Let me walk you through the most common causes and solutions:

🔍 Common Causes of Double Movement

Here are the typical reasons sprites move twice as far as intended:

flowchart TD A[🎮 Key Press Detected] --> B{Multiple Scripts?} B -->|Yes| C[❌ Duplicate Movement<br/>Both scripts run] B -->|No| D{Loop Issue?} D -->|Yes| E[❌ Movement in Loop<br/>Repeats multiple times] D -->|No| F{Clone Problem?} F -->|Yes| G[❌ Original + Clone<br/>Both move together] F -->|No| H{Variable Issue?} H -->|Yes| I[❌ Variable Changed<br/>During movement] H -->|No| J[✅ Check Other Causes] C --> K[🛠️ Remove Duplicate Scripts] E --> L[🛠️ Fix Loop Logic] G --> M[🛠️ Separate Clone Movement] I --> N[🛠️ Protect Variables] style C fill:#ffebee style E fill:#ffebee style G fill:#ffebee style I fill:#ffebee style K fill:#e8f5e8 style L fill:#e8f5e8 style M fill:#e8f5e8 style N fill:#e8f5e8

🔧 Debugging Step 1: Check for Duplicate Scripts

The most common cause is having multiple movement scripts running simultaneously:

    // BAD: Multiple scripts doing the same thing
when [right arrow v] key pressed
change x by (speed)

// Another script somewhere else:
when [right arrow v] key pressed
change x by (speed)

// RESULT: Sprite moves 2x speed because both scripts run!

Solution: Consolidate all movement into one script or use broadcasts:

    // GOOD: Single movement handler
when flag clicked
forever
if <key [right arrow v] pressed?> then
change x by (speed)
end
if <key [left arrow v] pressed?> then
change x by ((0) - (speed))
end
if <key [up arrow v] pressed?> then
change y by (speed)
end
if <key [down arrow v] pressed?> then
change y by ((0) - (speed))
end
end

🔄 Debugging Step 2: Check Loop Issues

Sometimes movement gets accidentally placed inside loops:

    // BAD: Movement inside a repeat loop
when [space v] key pressed
repeat [4] // This was your issue!
change x by (Xmov)
change y by (Ymov)
end

// RESULT: Moves 4 times instead of once!

Solution: Move the movement outside the loop or adjust the logic:

    // GOOD: Single movement per key press
when [space v] key pressed
change x by (Xmov)
change y by (Ymov)

// OR if you need the loop for animation:
when [space v] key pressed
set [total x v] to ((Xmov) / [4]) // Divide by loop count
set [total y v] to ((Ymov) / [4])
repeat [4]
change x by (total x)
change y by (total y)
wait [0.1] seconds // Smooth animation
end

👥 Debugging Step 3: Check Clone Conflicts

If you’re using clones, both the original and clone might be moving:

    // BAD: Both original and clone respond to keys
when flag clicked
create clone of [myself v]

when [right arrow v] key pressed
change x by (speed) // Both original AND clone move!

// SOLUTION: Use conditions to control who moves
when [right arrow v] key pressed
if <(clone id) = [player]> then // Only specific clone moves
change x by (speed)
end

🛠️ Debugging Step 4: Variable Protection

Sometimes variables get modified during movement:

    // BAD: Variable changes during movement
when [right arrow v] key pressed
change x by (speed)
change [speed v] by [1] // Oops! Speed increases each time

// GOOD: Protect movement variables
when [right arrow v] key pressed
set [move amount v] to (speed) // Save the value
change x by (move amount) // Use saved value
// Now it's safe to modify speed for other purposes

🔍 Debugging Tools

Use these techniques to identify the problem:

    // Add debugging output
when [right arrow v] key pressed
say (join [Moving by: ] (Xmov)) for [1] seconds
change x by (Xmov)
say (join [New X: ] (x position)) for [1] seconds

// Count how many times movement happens
when [right arrow v] key pressed
change [move counter v] by [1]
say (join [Move #] (move counter)) for [0.5] seconds
change x by (Xmov)

Based on your description, it sounds like you have a repeat loop around your movement code. Remove the loop or divide your movement values by the loop count! 🎯

MD

MovementDebugger

Replied 20 minutes later

@DebugMaster_Sam You nailed it! 🎯 It was exactly the repeat loop issue!

I had repeat (4) around my movement code, which was making the sprite move 4 times per key press. I removed the loop and now it works perfectly.

Thank you for the detailed debugging guide - I’ll definitely use those techniques for future issues!

GT

GameTester_Pro

Replied 1 hour later

Great debugging session! 👏 Here are some additional tips for preventing movement bugs:

🛡️ Movement Best Practices

  • Use a single movement script - Avoid multiple scripts handling the same keys
  • Test incrementally - Add movement features one at a time
  • Use meaningful variable names - player_speed instead of just speed
  • Add bounds checking - Prevent sprites from moving off-screen
    // Professional movement template
when flag clicked
set [player speed v] to [5]
forever
// Horizontal movement
if <key [right arrow v] pressed?> then
if <(x position) < [230]> then // Right boundary
change x by (player speed)
end
end
if <key [left arrow v] pressed?> then
if <(x position) > [-230]> then // Left boundary
change x by ((0) - (player speed))
end
end

// Vertical movement
if <key [up arrow v] pressed?> then
if <(y position) < [170]> then // Top boundary
change y by (player speed)
end
end
if <key [down arrow v] pressed?> then
if <(y position) > [-170]> then // Bottom boundary
change y by ((0) - (player speed))
end
end
end

Happy debugging! 🐛➡️✨

VB

Vibelf_Community

Pinned Message • Moderator

🚀 Master Professional Game Development

Excellent debugging discussion! For developers looking to create polished, bug-free games, our community can help you implement:

  • 🐛 Advanced debugging techniques
  • 🎮 Professional movement systems
  • 🔧 Code optimization strategies
  • ✅ Quality assurance practices

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