Creating a character jumping system in Scratch

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PlatformerDev_Sam

Posted on January 24, 2024 • Beginner

🦘 Need help making a character jump

Hi everyone! I’m trying to create a platformer game and I need help with the jumping mechanics. I want my character to jump when I press a key, but I’m not sure which blocks to use.

How do I make the character jump when a key is pressed?
How do I add gravity so the character falls back down?
How do I prevent the character from jumping while in the air?

I want to create smooth jumping like in Mario games! 🎮

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PhysicsMaster_Alex

Replied 1 hour later • ⭐ Best Answer

Great question @PlatformerDev_Sam! Jumping mechanics are fundamental to platformer games. Here’s a complete solution:

🦘 Jump Physics Flow

Here’s how the jumping system works:

flowchart TD A[🎮 Key Pressed] --> B{On Ground?} B -->|Yes| C[Start Jump] B -->|No| D[Ignore Input] C --> E[Set Y Velocity = Jump Power] E --> F[Apply Gravity Loop] F --> G[Move Up/Down by Y Velocity] G --> H[Reduce Y Velocity by Gravity] H --> I{Touching Ground?} I -->|No| J{Y Velocity > 0?} I -->|Yes| K[Land on Ground] J -->|Yes| L[Still Going Up] J -->|No| M[Falling Down] L --> F M --> F K --> N[Reset Y Velocity = 0] N --> O[Set On Ground = True] O --> P[Ready for Next Jump] D --> Q[Continue Current Motion] Q --> F style A fill:#e1f5fe style C fill:#f3e5f5 style K fill:#e8f5e8 style P fill:#fff3e0

🔧 Step 1: Create Variables

First, create these variables for your jumping system:

    // Create these variables
set [Y Velocity v] to [0]
set [On Ground v] to [1]
set [Jump Power v] to [15]
set [Gravity v] to [1]

🦘 Step 2: Basic Jump System

Main jumping script for your character:

    when flag clicked
forever
// Handle jump input
if <key [space v] pressed?> then
if <(On Ground) = [1]> then
set [Y Velocity v] to (Jump Power)
set [On Ground v] to [0]
play sound [jump v]
end
end

// Apply gravity and movement
change y by (Y Velocity)
change [Y Velocity v] by (0 - (Gravity))

// Ground collision detection
if <touching color [#8B4513]?> then // Brown ground color
repeat until <not <touching color [#8B4513]?>>
change y by [1]
end
set [Y Velocity v] to [0]
set [On Ground v] to [1]
end
end

🎯 Step 3: Improved Ground Detection

Better collision system using sprites instead of colors:

    // Ground detection with platforms
define check ground collision
if <touching [Ground v]?> then
if <(Y Velocity) < [0]> then // Only when falling
repeat until <not <touching [Ground v]?>>
change y by [1]
end
set [Y Velocity v] to [0]
set [On Ground v] to [1]
end
end

// Use in main loop
when flag clicked
forever
// Jump input
if <key [space v] pressed?> then
if <(On Ground) = [1]> then
set [Y Velocity v] to (Jump Power)
set [On Ground v] to [0]
end
end

// Physics
change y by (Y Velocity)
change [Y Velocity v] by (0 - (Gravity))

// Check collisions
check ground collision
end

🚀 Step 4: Advanced Features

Add variable jump height and coyote time:

    // Variable jump height
when flag clicked
set [Jump Held v] to [0]
forever
// Start jump
if <key [space v] pressed?> then
if <(On Ground) = [1]> then
set [Y Velocity v] to (Jump Power)
set [On Ground v] to [0]
set [Jump Held v] to [1]
end
else
set [Jump Held v] to [0]
end

// Reduce jump power if key released early
if <(Jump Held) = [0]> then
if <(Y Velocity) > [5]> then
set [Y Velocity v] to [5]
end
end

// Apply physics
change y by (Y Velocity)
change [Y Velocity v] by (0 - (Gravity))

check ground collision
end

🎮 Step 5: Coyote Time (Advanced)

Allow jumping for a short time after leaving the ground:

    // Coyote time system
set [Coyote Timer v] to [0]

forever
// Update coyote timer
if <(On Ground) = [1]> then
set [Coyote Timer v] to [6] // 0.1 seconds at 60 FPS
else
if <(Coyote Timer) > [0]> then
change [Coyote Timer v] by [-1]
end
end

// Jump with coyote time
if <key [space v] pressed?> then
if <<(On Ground) = [1]> or <(Coyote Timer) > [0]>> then
set [Y Velocity v] to (Jump Power)
set [On Ground v] to [0]
set [Coyote Timer v] to [0]
end
end

// Rest of physics code...
end

This creates smooth, responsive jumping that feels great to play! 🎮

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PlatformerDev_Sam

Replied 20 minutes later

@PhysicsMaster_Alex This is amazing! 🎉

The jumping works perfectly now! The variable jump height makes it feel so much more responsive. Thank you for the detailed explanation!

👍 Like (18)💬 Reply

GameDesigner_Maya

Replied 45 minutes later

Excellent tutorial! Here are some additional tips for polished jumping: