Guake is a top-down terminal for Gnome (in the style of Yakuake for KDE, Tilda or the terminal used in Quake). See the official website at Guake-project.org.
You can check the screenshots to get a small feeling about it.
How to get it
Guake is packaged by a number of distributions, among which are Fedora, Debian, Ubuntu or ArchLinux, so please check your repo. Source tarballs are available; see the Release page.
Available at https://guake.readthedocs.io/en/stable/
If you starve to add a feature to Guake, head to the repo. Some knowledge of Python, git and GTK is all what you need.