Store Closed Module for OpenCart is built with the ability to allow the owner of the store to restrict customer access to the front end of the store but allows access to the back end to manage products, orders, and other important store functions. The administrators can also show a custom message or page during the closure period with an estimated date of reopening, if needed.

Key Features:

1. Maintenance Mode Activation:
   • A single toggle to activate a maintenance or "store closed" mode blocks customers from the store. 
2. Customisable Messages:
   • Create a display page or message to customers indicating the business is closed temporarily and may state the reason for the business's temporary closing or when it will reopen. 
3. Reopening Countdown:
   • Add a countdown timer to let customers know when the store will be accessible again, which can help manage customer expectations and retain interest. 
4. IP Whitelisting:
   • Allow specific IP addresses (like admin or developers' IPs) to bypass the store closed mode, enabling access for testing or troubleshooting without disrupting customer-facing interactions. 
5. Admin-Only Access:
   • The visibility of the store is only allowed to admins so they can continue making changes, updates, or monitoring store performance during downtime. 
6. Notification Options:
   • Options for sending email or popup notifications to customers about the store status so that they get advanced notice of closure periods ahead. 
7. Custom Themes and Design:
   • Customises the "store closed" page so that it would fall into place with brand colours and designs so as to appear professional despite closure. 

Benefits:

1. Efficient Maintenance Management:
   • Store owners can perform updates, manage inventory, or resolve technical issues without affecting customer experience, hence ensuring the smooth running of maintenance operations. 
2. Professional Communication:
   • The customisable message and countdown options offer a professional approach to downtime, creating customer trust by keeping them informed.
3. Reduced Customer Frustration:
   • Customer frustration is reduced because customers are not met with broken pages or errors but clear communication about the closure, making them more likely to return once the store reopens. 
4. Enhanced Security:
   • Only certain IP addresses are allowed to provide safety for sensitive information, along with safe backend access while lowering the risks involved with maintenance. 
5. Improved Customer Retention:
   • Countdown timers and custom messages convey the temporary nature of the store closure, thus maintaining interest among the customers to revisit when the store reopens again. 
6. Brand Consistency:
   •  The customisation of the closure page ensures that even when the store is down, the brand image is maintained, and customers are kept engaged. 
7. Reduced Lost Sales:
   • Because the customer is informed of when the store will reopen, the customer is likely to come back and make purchases, reducing the chance of losing sales due to maintenance.