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Fixing clone multiplication bugs in Scratch games

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CM

CloneMaster_Dev

Posted on January 30, 2024 • Intermediate

🌱 Clone multiplication bug in my garden game

Hey debugging experts! I’m working on a garden simulation game where players can plant seeds that grow into plants. However, I’m experiencing a weird clone multiplication bug that’s driving me crazy!

The Problem:

  • 1st plant: Creates 1 clone (correct)
  • 2nd plant: Creates 2 clones (should be 1)
  • 3rd plant: Creates 4 clones (should be 1)
  • 4th plant: Creates 8 clones (should be 1)
  • And it keeps doubling exponentially!

It looks like only one plant appears visually, but when I check my clone counter, the numbers are going crazy. Each time I plant a new seed, the clone count doubles instead of just adding one.

Has anyone encountered this before? I suspect it has something to do with broadcasts, but I can’t figure out the exact cause. Help! 🆘

DB

DebugMaster_Sarah

Replied 1 hour later • ⭐ Best Answer

I know exactly what’s happening @CloneMaster_Dev! This is a classic clone multiplication bug. The issue is that your broadcast is being received by ALL clones, not just the original sprite.

🔍 The Root Cause

When you broadcast a message to create a clone, every existing clone also receives that broadcast and creates its own clone. This creates exponential growth:

  • 1st plant: Original sprite creates 1 clone
  • 2nd plant: Original sprite + 1 clone both create clones = 2 total
  • 3rd plant: Original sprite + 2 clones all create clones = 4 total
  • 4th plant: Original sprite + 4 clones all create clones = 8 total

✅ Solution 1: Clone ID System

Use a “for this sprite only” variable to identify the original sprite:

    // Create a 'for this sprite only' variable called 'clone ID'
when flag clicked
set [clone ID v] to [0]  // Original sprite has ID 0

when I start as a clone
set [clone ID v] to [1]  // All clones have ID 1
// Other clone initialization code here

when I receive [plant seed v]
if <(clone ID) = [0]> then
// Only the original sprite creates clones
create clone of [myself v]
change [plants created v] by [1]
end

✅ Solution 2: Direct Cloning

Instead of using broadcasts, clone directly from the sprite that needs to create the clone:

    // In your main game sprite (not the plant sprite)
when I receive [plant button clicked v]
if <(seeds) > [0]> then
// Clone the plant sprite directly
broadcast [create plant at v] and wait
change [seeds v] by [-1]
end

// In your plant sprite
when I receive [create plant at v]
if <not <(clone ID) = [0]>> then
stop [this script v]  // Prevent clones from responding
end
create clone of [myself v]

✅ Solution 3: Advanced Clone Management

For complex games, use a centralized clone manager:

    // Clone Manager Sprite
when flag clicked
set [next clone ID v] to [1]
set [active clones v] to []

define create plant clone (x) (y) (type)
broadcast [prepare clone v]
wait (0.1) seconds
create clone of [Plant v]
add (next clone ID) to [active clones v]
change [next clone ID v] by [1]

// In Plant Sprite
when I receive [prepare clone v]
if <(clone ID) = [0]> then
set [pending clone data v] to (join (mouse x) (join [,] (mouse y)))
end

when I start as a clone
set [clone ID v] to (next clone ID)
set [my x v] to (item 1 of (pending clone data))
set [my y v] to (item 2 of (pending clone data))
go to x: (my x) y: (my y)
show

🛠️ Debugging Tips

To help debug clone issues in the future:

    // Add this to your clone sprite for debugging
when I start as a clone
say (join [Clone ID: ] (clone ID)) for (2) seconds

// Count total clones
when flag clicked
forever
set [total clones v] to [0]
broadcast [count clones v] and wait
wait (1) seconds
end

when I receive [count clones v]
change [total clones v] by [1]

🎯 Prevention Best Practices

  • Always use clone IDs: Distinguish between original sprites and clones
  • Limit broadcast scope: Use “broadcast and wait” when order matters
  • Clean up clones: Delete clones when they’re no longer needed
  • Test incrementally: Add one feature at a time to catch bugs early

This should completely solve your clone multiplication problem! 🎯

CM

CloneMaster_Dev

Replied 30 minutes later

@DebugMaster_Sarah You’re a lifesaver! 🙌

The clone ID solution worked perfectly! I implemented it and now each plant creates exactly one clone as expected. I can’t believe such a simple variable could solve such a complex-seeming problem.

The debugging tips are also super helpful - I can now see exactly what each clone is doing. Thank you so much!

GD

GameDev_Pro

Replied 2 hours later

This is such a common bug! I’ve seen it in countless student projects. Here’s an additional tip for managing large numbers of clones:

    // Clone pool system for better performance
when flag clicked
set [clone pool v] to []
set [active clones v] to []
set [inactive clones v] to []

// Pre-create a pool of clones
repeat (50)
create clone of [Plant v]
end

define get clone from pool
if <(length of [inactive clones v]) > [0]> then
set [clone to use v] to (item 1 of [inactive clones v])
delete (1) of [inactive clones v]
add (clone to use) to [active clones v]
broadcast (join [activate clone ] (clone to use))
else
// Create new clone if pool is empty
create clone of [Plant v]
end

This prevents creating too many clones and improves performance! 🚀

VB

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