base-apparel-coming-soon page using CSS flexbox and sass/scss

Hi, it's my 3rd challenge here. (English is not my main language, sorry for mistakes) All comments are very appreciated. Actually, I think this layout is a bit higher than newbie level (or at least for me). Furthermore, I created this page with sass/scss, and css flexbox. But I'm not sure whether flexbox is a right choice or not. Again, thank you for everyone who leaves a comment here.