The Mint-Y theme provides users with a modern flat design, but it looks like it won’t be the default for the Linux Mint 18 “Sarah” operating system, which will sport the same default look like the one of Linux Mint 17.3 “Rosa,” based on the Mint-X theme. Why? Simply because the Linux Mint devs don’t want to force the new look on users. They want Mint-Y to be an alternative look for Linux Mint 18, and if users’ feedback proves to be positive, then they might consider enabling it by default for Linux Mint 18.1.