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How to prevent negative money in shop systems

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SB

ShopBuilder_Dev

Posted on January 22, 2024 • Beginner

🛒 Shop system money validation help needed

Hi everyone! I’m building a game with a shop system where players can buy upgrades and items. The problem is that when players don’t have enough money, the purchase still goes through and their money goes into negative numbers! 😅

I need help implementing a system that:

  • Checks if the player has enough money before allowing a purchase
  • Prevents the money from going below zero
  • Shows an error message when they can’t afford something
  • Only completes the purchase if they have sufficient funds

I’m still learning about conditional statements and variables. Any guidance would be super helpful! 🙏

GP

GameProgrammer_Alex

Replied 1 hour later • ⭐ Best Answer

Great question @ShopBuilder_Dev! Money validation is crucial for any shop system. Here’s a comprehensive solution:

🔧 Step 1: Basic Money Check

The fundamental check before any purchase:

    when this sprite clicked
if <(money) >= (item price)> then
change [money v] by ((item price) * (-1))
change [item count v] by [1]
play sound [purchase success v]
say [Item purchased!] for [2] seconds
else
play sound [error v]
say [Not enough money!] for [2] seconds
end

🛡️ Step 2: Advanced Validation System

For a more robust shop system with multiple items:

    // Custom block: attempt purchase
define attempt purchase (price) (item name)
if <(money) >= (price)> then
change [money v] by ((price) * (-1))
broadcast (join [buy ] (item name))
play sound [coin v]
set [purchase result v] to [success]
else
set [purchase result v] to [failed]
play sound [error beep v]
say (join [Need ] (join ((price) - (money)) [ more coins!])) for [3] seconds
end

💡 Step 3: Shop Interface with Visual Feedback

Create a visual shop interface that shows affordability:

    when flag clicked
forever
// Update item affordability display
if <(money) >= (sword price)> then
set [sword color v] effect to [0]
set [sword text v] to [BUY SWORD - 100 coins]
else
set [sword color v] effect to [50]
set [sword text v] to [SWORD - 100 coins (Can't afford)]
end

if <(money) >= (shield price)> then
set [shield color v] effect to [0]
set [shield text v] to [BUY SHIELD - 250 coins]
else
set [shield color v] effect to [50]
set [shield text v] to [SHIELD - 250 coins (Can't afford)]
end
end

🎯 Step 4: Complete Shop System Example

Here’s a complete shop system for a sword item:

    // On sword shop button
when this sprite clicked
set [item price v] to [100]
set [item name v] to [Sword]

if <(money) >= (item price)> then
// Successful purchase
change [money v] by ((item price) * (-1))
change [sword count v] by [1]

// Visual feedback
play sound [purchase v]
create clone of [coin effect v]
say [Sword purchased! +1 Attack] for [2] seconds

// Update player stats
change [attack power v] by [10]

else
// Failed purchase
play sound [error v]
set [needed coins v] to ((item price) - (money))
say (join [Need ] (join (needed coins) [ more coins!])) for [3] seconds

// Shake effect for denied purchase
repeat [5]
change x by [5]
wait [0.1] seconds
change x by [-5]
wait [0.1] seconds
end
end

🚀 Pro Tips for Shop Systems

  • Always check first: Never subtract money before checking if they have enough
  • Use variables for prices: Makes it easy to adjust prices later
  • Provide clear feedback: Tell players exactly how much more they need
  • Visual indicators: Gray out items they can’t afford
  • Sound effects: Different sounds for success vs failure

This system ensures your players never go into debt and always know what they can afford! 💪

SB

ShopBuilder_Dev

Replied 45 minutes later

@GameProgrammer_Alex This is exactly what I needed! 🎉 The visual feedback system is brilliant!

I implemented the basic version and it works perfectly. One question though - how do I handle bulk purchases where players might want to buy multiple items at once?

EC

EconomyExpert_Sam

Replied 1 hour later

@ShopBuilder_Dev Great question about bulk purchases! Here’s how to handle quantity-based buying:

    // Bulk purchase system
define buy multiple (item price) (quantity)
set [total cost v] to ((item price) * (quantity))

if <(money) >= (total cost)> then
change [money v] by ((total cost) * (-1))
change [item count v] by (quantity)
say (join [Bought ] (join (quantity) [ items!])) for [2] seconds
else
set [max affordable v] to (round ((money) / (item price)))
say (join [Can only afford ] (join (max affordable) [ items])) for [3] seconds
end

This way players know exactly how many they can afford! 💰

VB

Vibelf_Community

Pinned Message • Moderator

🛒 Master Advanced Shop Systems

Excellent discussion on shop validation! For developers ready to create even more sophisticated commerce systems, our community can help you implement:

  • 🏪 Multi-currency systems
  • 🎁 Dynamic pricing and discounts
  • 📦 Inventory management
  • 🔄 Refund and return systems
  • 💎 Premium item unlocks

📚 Related Topics

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