Make volume and brightness OSDs horizontal on your Cinnamon desktop environment. It's customizable so you can make your own OSDs too.
Alongside making your OSDs horizontal, there are lots of configuration options so you can customize OSDs as you want. Such as:
- Position, size, border-radius and hide timeout of osd window
- Size of icon, label and level bar
- border-radius of level bar
Also you can write your custom CSS for all those elements.