Here are a couple of things I picked up from taking a look at your code:
I'd recommend using margin in your CSS to space out elements instead of using multiple <br /> tags in your HTML. This will help clean up your HTML quite a bit and allow for more precise spacing.
Also, where possible I'd choose HTML5 structural elements over div elements. Adding elements such as header, section and main provide structure to your markup.
Your CSS is really nice and concise. Bulma is a great CSS framework to use! For your .ios-button and .mac-button classes you could share a lot of those styles under a single class and then change the colours using a modifier class.
I hope those suggestions help! Let me know if you have any questions.
Keep up the great work!
Thanks a lot for the feedback, Matt! Those are super helpful tips! Excited to get your feedback on my next solution.