I got to make the panels smaller in width, and also added a rounded border on then.
Since i don't really created a new cinnamon theme (is just some hardcoded changes on mint-y-dark-purple cinnamon.css), i don't have a source code to share, sorry twt.
But here is what i've done:
Copy and pasted the theme in /usr/share/themes to ~/.themes, so its easier to edit.
Then i changed some rules on the following selectors:
.panel-top {
/* This is what makes the gap in every size of the pannel */
margin-left: 150px;
margin-right: 150px;
padding-left: 15px;
padding-right: 15px;
border-radius: 0 0 15px 15px;
}
/* you can set a value for each class */
.panel-bottom {
margin-left: 300px;
margin-right: 300px;
padding-left: 15px;
padding-right: 15px;
border-radius: 30px 30px 0 0;
}
Theres some changes on the menu too, but i would need some more time to compile all the changes i made.
Also, these changes are hardcoded on cinnamon.css, so, it may not work for every computer, every screensize, and so on and so on, so i don't think this should be just a theme.
I'm planning to create a cinnamon extension to make these changes, but i still don't know how to change cinnamon.css on the fly using a extension, so, it still just an idea.
Anyways, hope you guys like what i've done :)