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Basic Ground Collision System for Platformers

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PB

PlatformerBuilder_Sam

Posted on January 8, 2025 • Beginner

🏗️ Need help with basic ground collision system

Please help! I need a basic (preferably simple) code for ground collision in platformers. I want to create my own platformer from scratch but I’m struggling with:

  • Making the player stop when touching the ground
  • Preventing the player from falling through platforms
  • Allowing the player to jump only when on ground
  • Simple gravity system

I’ve seen other platformers but I want to understand how to build this myself. Please give the code as if it’s for a platformer to make understanding easy! 🙏

CD

CollisionDetective_Pro

Replied 15 minutes later • ⭐ Best Answer

Perfect question @PlatformerBuilder_Sam! Ground collision is fundamental to platformers. Here’s a simple but effective system:

📊 Ground Collision System Flow

Here’s how the ground collision detection works:

flowchart TD A[🎮 Game Start] --> B[Initialize Variables] B --> C[Set Y Velocity = 0] C --> D[Set Can Jump = 0] D --> E[🔄 Game Loop] E --> F{Touching Ground?} F -->|Yes| G[Push Player Up] F -->|No| H[Apply Gravity] G --> I[Set Y Velocity = 0] I --> J[Set Can Jump = 1] J --> K{Jump Key Pressed?} H --> L[Increase Y Velocity] L --> M[Move Player Down] M --> N[Set Can Jump = 0] K -->|Yes & Can Jump| O[Set Y Velocity = -15] K -->|No| P[Stay on Ground] O --> Q[Set Can Jump = 0] P --> E Q --> E N --> E style A fill:#e1f5fe style B fill:#f3e5f5 style F fill:#e8f5e8 style G fill:#fff3e0 style H fill:#fce4ec

🎨 Step 1: Set Up Your Ground

First, create your ground sprites or use a specific color for ground detection. I recommend using a bright green color (#00FF00) that you can easily identify.

📦 Step 2: Create Essential Variables

Create these variables for your player sprite:

  • Y Velocity - Controls how fast the player falls
  • Can Jump - Tracks if player can jump (1 = yes, 0 = no)

🔧 Step 3: Basic Ground Collision System

Here’s the core collision detection code:

    when flag clicked
set [Y Velocity v] to [0]
set [Can Jump v] to [0]
forever
// Check if touching ground color
if <touching color [#00FF00]?> then
// Push player up slightly to get out of ground
change y by [2]
// Stop falling
set [Y Velocity v] to [0]
// Allow jumping
set [Can Jump v] to [1]
else
// Apply gravity when not on ground
change [Y Velocity v] by [-0.5]
// Can't jump in air
set [Can Jump v] to [0]
end

// Apply vertical movement
change y by (Y Velocity)
end

⌨️ Step 4: Jump Controls

Add this script for jumping:

    when flag clicked
forever
if <key [space v] pressed?> then
if <(Can Jump) = [1]> then
set [Y Velocity v] to [10]
set [Can Jump v] to [0]
play sound [jump v]
end
end
end

🏃 Step 5: Horizontal Movement

For left and right movement:

    when flag clicked
forever
if <key [left arrow v] pressed?> then
change x by [-3]
end
if <key [right arrow v] pressed?> then
change x by [3]
end
end

🚀 Step 6: Enhanced Version (Optional)

For better collision detection, you can use sprite-based ground instead of color:

    when flag clicked
forever
// Check if touching ground sprite
if <touching [Ground v]?> then
// Move up until not touching
repeat until <not <touching [Ground v]?>>
change y by [1]
end
set [Y Velocity v] to [0]
set [Can Jump v] to [1]
else
change [Y Velocity v] by [-0.5]
set [Can Jump v] to [0]
end

change y by (Y Velocity)
end

💡 Pro Tips:

  • Ground Color: Use a bright, unique color that doesn’t appear elsewhere in your game
  • Gravity Value: Adjust -0.5 to make gravity stronger (more negative) or weaker (less negative)
  • Jump Height: Change the jump velocity (10) to make jumps higher or lower
  • Movement Speed: Adjust the horizontal movement values (3) for faster or slower movement

This system gives you a solid foundation for any platformer! 🎮

PB

PlatformerBuilder_Sam

Replied 20 minutes later

@CollisionDetective_Pro Thank you for that amazing explanation! 🎉

This is exactly what I needed! The code works perfectly and I finally understand how ground collision works. I love how you explained each part step by step.

Now I can finally create my own platformer from scratch instead of just remixing others! 🚀

VB

Vibelf_Community

Pinned Message • Moderator

🚀 Ready to Build Amazing Platformers?

Great foundation discussion on ground collision! For those looking to expand their platformer skills, our community can help you implement:

  • 🎯 Advanced collision detection for slopes and curves
  • 🌟 Moving platforms and elevators
  • 🎨 Multiple ground types with different properties
  • 🏆 One-way platforms and wall jumping

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