跳转到内容

Fixing Top-Down Enemy Movement Issues in Scratch

此内容尚不支持你的语言。

💡 Struggling with enemy AI and movement systems? Need help with top-down game mechanics? 🚀 Get Help Now

AK

ActionKid_Dev

Posted on August 4, 2025 • Advanced

🤖 Top-down enemy movement problems

Hey everyone! I’ve been working on a top-down game for over a year, and enemy movement has been my biggest challenge. I’m using a system based on Griffpatch’s approach, but I’m running into a specific issue:

  • Enemy clones disappear after moving a certain distance
  • It’s not an onScreen variable issue
  • The movement system seems to push clones outside the level boundaries
  • This happens consistently after traversing a specific distance

I’ve isolated the enemy scripts to test this issue, but I can’t figure out what’s causing the movement to go wrong. Any help would be greatly appreciated! 🙏

TD

TopDownExpert

Replied 2 hours later • ⭐ Best Answer

Great question @ActionKid_Dev! This is a very common issue with top-down enemy systems. The problem you’re describing usually stems from accumulating movement errors or boundary detection issues. Let me help you fix this:

🔍 Step 1: Identify the Root Cause

The “disappearing” enemies are likely being pushed outside the level due to movement calculation errors. Here’s how to diagnose and fix it:

    // Add debug tracking to your enemy movement
when I start as a clone
set [debug mode v] to [1] // Turn this on for testing
forever
if <(debug mode) = [1]> then
say (join [X: ] (join (round (x position)) (join [ Y: ] (round (y position)))))
end
// Your existing movement code here
end

🎯 Step 2: Fix Movement Calculation

Replace your current movement system with this more stable approach:

    // Improved enemy movement system
define move towards player
set [target x v] to ([x position v] of [Player v])
set [target y v] to ([y position v] of [Player v])
set [distance to player v] to (distance to [Player v])

// Calculate movement direction
set [dx v] to ((target x) - (x position))
set [dy v] to ((target y) - (y position))

// Normalize movement (prevent speed issues)
if <(distance to player) > [0]> then
set [move x v] to (((dx) / (distance to player)) * (enemy speed))
set [move y v] to (((dy) / (distance to player)) * (enemy speed))
else
set [move x v] to [0]
set [move y v] to [0]
end

// Apply movement with boundary checking
change x by (move x)
if <touching [walls v]?> then
change x by ((-1) * (move x))
end

change y by (move y)
if <touching [walls v]?> then
change y by ((-1) * (move y))
end

🚧 Step 3: Add Boundary Protection

Prevent enemies from going outside the level:

    // Boundary protection system
define check boundaries
// Define your level boundaries
set [level left v] to [-400]
set [level right v] to [400]
set [level top v] to [300]
set [level bottom v] to [-300]

// Keep enemy within bounds
if <(x position) < (level left)> then
set x to (level left)
end
if <(x position) > (level right)> then
set x to (level right)
end
if <(y position) < (level bottom)> then
set y to (level bottom)
end
if <(y position) > (level top)> then
set y to (level top)
end

// Call this after every movement
move towards player
check boundaries

🔄 Step 4: Improve Clone Management

Add proper clone lifecycle management:

    // Enhanced clone management
when I start as a clone
set [clone id v] to (length of [active enemies v])
add (clone id) to [active enemies v]
set [enemy health v] to [100]
set [last position x v] to (x position)
set [last position y v] to (y position)

forever
// Movement code here
move towards player
check boundaries

// Safety check - if enemy moves too far from last valid position
if <(distance to x: (last position x) y: (last position y)) > [200]> then
// Reset to last known good position
go to x: (last position x) y: (last position y)
else
// Update last known good position
set [last position x v] to (x position)
set [last position y v] to (y position)
end

// Check if enemy should be deleted
if <<(enemy health) < [1]> or <(distance to [Player v]) > [800]>> then
delete (item # of (clone id) in [active enemies v]) of [active enemies v]
delete this clone
end
end

⚡ Step 5: Optimize Performance

Add performance optimizations to prevent lag-related movement issues:

    // Performance optimization
when I start as a clone
forever
// Only update movement if player is nearby
if <(distance to [Player v]) < [400]> then
move towards player
check boundaries
else
// Simple movement when far away
point towards [Player v]
move [1] steps
check boundaries
end

// Reduce update frequency for distant enemies
if <(distance to [Player v]) > [200]> then
wait [0.1] seconds
end
end

🛠️ Step 6: Debug Tools

Add these debug tools to help identify issues:

    // Debug visualization
when [space v] key pressed
if <(debug mode) = [1]> then
set [debug mode v] to [0]
else
set [debug mode v] to [1]
end

// In your enemy clone
when I start as a clone
forever
if <(debug mode) = [1]> then
pen down
set pen color to [#ff0000]
set pen size to [2]
else
pen up
end
end

Try implementing these fixes step by step. The boundary protection and movement normalization should solve your disappearing enemy issue! Let me know if you need help with any specific part! 🎮

GP

GriffpatchFan_Dev

Replied 1 hour later

@TopDownExpert gave excellent advice! I’ve worked with Griffpatch’s systems extensively, and this issue usually happens when:

  • Movement accumulation errors: Small rounding errors add up over time
  • Missing boundary checks: Enemies can slip through walls due to high speeds
  • Clone ID conflicts: Multiple clones trying to use the same variables

One quick fix that often helps is adding a “safety reset” mechanism:

    // Safety reset for lost enemies
when I start as a clone
set [safety timer v] to [0]
forever
change [safety timer v] by [1]
if <(safety timer) > [600]> then // 10 seconds at 60 FPS
if <(distance to [Player v]) > [600]> then
// Reset enemy to a safe spawn point
go to x: (pick random [-200] to [200]) y: (pick random [-200] to [200])
set [safety timer v] to [0]
end
end
end

This prevents enemies from getting permanently lost! 🎯

AK

ActionKid_Dev

Replied 45 minutes later

@TopDownExpert @GriffpatchFan_Dev This is incredibly helpful! Thank you both! 🎉

I can see now that I was missing proper boundary checks and the movement normalization. The debug tools will be really useful for tracking down these issues. Going to implement these fixes right away!

VB

Vibelf_Community

Pinned Message • Moderator

🚀 Master Advanced Enemy AI Systems?

Great discussion on top-down enemy movement! For those looking to create even more sophisticated enemy behaviors, our community can help you implement:

  • 🧠 Advanced pathfinding algorithms
  • 🎯 Smart targeting and prediction systems
  • 🤖 State-based enemy AI behaviors
  • ⚡ Performance-optimized enemy systems

📚 Related Discussions

Ready to create intelligent enemy systems? Get expert guidance from our AI specialists in the Vibelf app!