Karol Brennan Headshot

Hi! My name is Karol Brennan

I'm a web developer from Milwaukee, Wisconsin

I created a bingo calling application called letsplaybingo.io that is used to run bingo games around the world.

I'm currently building highly customized sites in Salesforce Experience Cloud at Slalom.

Recent things I've worked on.

After spending the last several years working within consulting the vast majority of what I have built is proprietary. If you have any questions about the types of projects I've been involved in please ask!

I do maintain some open source work on my GitHub if you'd like to check out some of my code.

Let's Play Bingo

Let's Play Bingo screenshot


Creator / Sole Developer
Live Site

Originally created in 2017 as a vanilla Javascript application, I rebuilt it in ReactJS in 2018. Then I rewrote it again in 2020, and yet again in 2023 (private repo). I'm always improving on it and adding new features. It's where I hone my skills and keep things fresh. Let's Play Bingo has grown to have over a million lifetime users and is now the #1 bingo caller on Google! It is used by over 50,000 users each month in over 180 countries to facilitate games at home with friends or in bingo halls.

ReactJS Sass Javascript HTML5 CSS3

Databricks Partner Directory

Databricks screenshot

Salesforce Experience Cloud

Senior Consultant / Developer @ Slalom
Live Site | Slalom Case Study

I was brought on as a developer during my employment with Slalom for the Databricks project. I was tasked with building many custom features of the portal with the largest undertaking being the public facing Partner Directory. I personally built all of the functionality shown in the directory including custom search with filters, pagination and the individual listing pages.

Apex Lightning Web Components HTML5 CSS3 Javascript

Hulu Community


Salesforce Experience Cloud

Senior Front-End Developer @ 7Summits, an IBM company
Live Site

I built many custom features across 3 years of partnering with Hulu. During my final months at 7Summits and on the Hulu project team I worked closely with another developer and together we built a completely custom Salesforce chatter feed which you can see in action in the Questions and Community News portions of the site.

Apex Lightning Web Components Aura HTML5 CSS3 Javascript

Additional projects

Salesforce Experience Cloud

Senior Front-End Developer @ 7Summits, an IBM Company

Built a custom document center for a customer portal that enabled users to manage their documents. Within this interface users could drag and drop or select files to upload, change file names and indicate the type of files being uploaded as well as review their submissions.

Apex Aura Lightning Web Components HTML5 CSS3 Javascript

Salesforce Experience Cloud

Senior Front-End Developer @ 7Summits, an IBM company

Partner community implementation for a top technology company that enabled partners to create customer success stories that would be converted into downloadable PDFs.

Apex Aura HTML5 CSS3 Javascript

Salesforce Experience Cloud

Front-End Developer @ Canpango

Partner community implementation for a large automotive manufacturer that enabled their dealers to generate customized direct mail pieces to their customers.

Apex Aura HTML5 CSS3 Javascript

My Current Roles

A Girl Created This, LLC

Owner / Developer

May 2020 - Current

Developed the #1 “free bingo caller” application on Google called Let's Play Bingo.

  • Originally written in January 2017 using pure object oriented JavaScript.
  • Refactored to a single page ReactJS app in 2018 leveraging Sass and a custom grid system.
  • LPB currently receives an average of 40k users per month across 180+ countries.


Senior Consultant / Developer

May 2022 - Current

Served as a subject matter expert on the Salesforce Experience Cloud team.

  • Developed highly customized Salesforce Experience Cloud sites for a variety of clients.
  • Established an internal component respository used to accellerate project development.
  • Established coding standards for the team and drove conversations surrounding best practices.
If you're interested in my full professional history, check out my LinkedIn profile.

You can also download a copy of my full resume.

A little more about me.

Throughout my career I've worked as a Salesforce developer, front-end / ReactJS developer, full stack PHP developer, and web designer. I found my passion in bringing designs to pixel perfect fruition on the front-end through HTML, CSS and JavaScript.

I am a minimalistic developer, prefering to use vanilla JavaScript and plain CSS when possible. I only reach for a framework when there is something to gain from them. Usually for more complex component driven projects. My current framework of choice is ReactJS, which I have been using for my side project letsplaybingo.io since 2018. I often employ Sass for CSS pre-processing and like to use my own simple grid system in my personal work instead of something like Foundation or Bootstrap. I enjoy component driven development, object oriented programming concepts, and new challenges that require abstraction and data manipulation.

Outside of my career - I am happily married and I am the proud mama of 2 awesome kids. I believe in equality, kindness, and helping others. I care about sustainability, animal rights, and human welfare. In my spare time I enjoy spending time with my family and copious amounts of gaming. I run on plants, water, and sarcasm.

Let's connect!

Check out my full resume.
Connect with me on LinkedIn.
Follow my open source work on GitHub.
Wanna chat about something else? Send an email to hello at karol.dev.