# Dunlin - a extensible Fennel-based web browser > The dunlin (Calidris alpina) is a small wader. It is a circumpolar > breeder in Arctic or subarctic regions. Birds that breed in northern > Europe and Asia are long-distance migrants, wintering south to Africa, > southeast Asia and the Middle East. Birds that breed in Alaska and the > Canadian Arctic migrate short distances to the Pacific and Atlantic > coasts of North America, although those nesting in northern Alaska > overwinter in Asia. Dunlin is a GTK-based Webkit browser which can be extended in (indeed, is mostly written in) [Fennel](https://www.fennel-lang.org). ## Hacking $ nix-shell nix-shell$ overmind start -D nix-shell$ overmind connect This starts a Fennel interpreter and a test runner in tmux windows. Use `C-b n` to switch between them or `C-b d` to detach. $ fennel dunlin.fnl & $ ./repl.sh Dunlin will open a socket in `$XDG_RUNTIME_DIR` to allow communication with a Fennel REPL. The repl.sh script uses [socat](http://www.dest-unreach.org/socat/) to connect to it.