Code an Application that Password Protects Individual Pages and Collections on our Shopify Site

I'd like to be able to password protect individual product and collection pages on our Shopify site. This should be formatted as a pop-up light box that prompts for a password. The pop-up should allow for simple customizing of colors and font and messaging - and look visually pleasing. If an entire collection is protected, the collection page should be protected. If an individual product is protected, the individual product's page should be protected. This should be able to be tested in your own shopify environment, with instructions on how to upload the code to our own site when the project is complete. The app should ultimately "live" entirely within our own shopify environment. The milestone will be awarded once the application has been proven to work in our own development environment.