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Fixing "Go to" block lag in Scratch platformer games

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PA

PlatformerDev_Alex

Posted on April 5, 2019 • Intermediate

🎮 Costume sprite lagging behind character in platformer

Hey everyone! I’m working on a platformer game where players can choose different costumes for their character. To keep things organized, I created a separate sprite for the costumes that follows the main character using this script:

when green flag clicked
forever
  go to [character v]
end

The problem is that the costume sprite lags behind the character sprite by about one frame. It works fine when I manually restart the script, but the lag returns when I use the green flag or stop/start the project. This is especially noticeable in the published version.

Has anyone encountered this issue before? Any suggestions would be really helpful! 🙏

SC

ScratchCoder_Pro

Replied 4 hours later • ⭐ Best Answer

Great question @PlatformerDev_Alex! This is a classic script execution order issue that many developers encounter. Here’s what’s happening and how to fix it:

🔍 Understanding the Problem

The lag occurs because Scratch doesn’t guarantee the order in which scripts execute within the same frame. Your character sprite might move after the costume sprite has already updated its position, causing the one-frame delay.

sequenceDiagram participant F as Frame Start participant C as Costume Sprite participant P as Player Sprite participant S as Screen Update Note over F,S: Problem: Costume updates before Player moves F->>C: go to [player] F->>P: move player P->>S: Screen shows costume at old position Note over F,S: Solution: Control execution order F->>P: move player first P->>C: then update costume position C->>S: Screen shows synchronized sprites

🛠️ Solution 1: Broadcast Control (Recommended)

Use broadcasts to control the execution order. Here’s the setup:

Main Control Script (on Stage or any sprite):

    when flag clicked
forever
broadcast [update player v]
broadcast [update costume v]
end

Player Sprite:

    when I receive [update player v]
// Your player movement code here
change x by (speed)
if <key [space v] pressed?> then
change y by [10]
end

Costume Sprite:

    when I receive [update costume v]
go to [player v]

🛠️ Solution 2: Single Sprite Control

Alternatively, let the player sprite control the costume directly:

Player Sprite:

    when flag clicked
forever
// Movement code
change x by (speed)

// Update costume position immediately
broadcast [move costume v]
end

Costume Sprite:

    when I receive [move costume v]
go to [player v]

🎯 Pro Tips for Smooth Synchronization

  • Consistent timing: Always use the same control method throughout your project
  • Minimize scripts: Fewer forever loops = more predictable execution
  • Test thoroughly: Check both editor and published versions
  • Consider alternatives: Sometimes using costumes instead of separate sprites is simpler

This approach ensures your costume sprite will always be perfectly synchronized with your character! 🎮✨

PA

PlatformerDev_Alex

Replied 45 minutes later

@ScratchCoder_Pro This is exactly what I needed! 🎉

The broadcast method worked perfectly - no more lag issues! I used Solution 1 and now both sprites move in perfect sync. Thanks for the detailed explanation and the diagram, it really helped me understand what was happening behind the scenes.

One quick follow-up: should I be worried about performance with all these broadcasts?

SC

ScratchCoder_Pro

Replied 20 minutes later

@PlatformerDev_Alex Great question about performance! 👍

Broadcasts are actually very efficient in Scratch. The overhead is minimal, especially for a simple setup like yours. You’d need hundreds of broadcasts per frame before noticing any performance impact.

For your platformer, this approach is much better than having multiple uncontrolled forever loops competing for execution time. Keep using it! 🚀

VB

Vibelf_Community

Pinned Message • Moderator

🚀 Master Advanced Game Synchronization!

Excellent discussion on sprite synchronization! For developers looking to create even more sophisticated platformers, our community can help you implement:

  • 🎯 Multi-sprite coordination systems
  • ⚡ Performance optimization techniques
  • 🎮 Advanced platformer mechanics
  • 🔄 State management patterns

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