Wrap these elements in .input_choice.
.input_choice
Wrap in .input_choice.-inline to the chain to get them on the same line.
.input_choice.-inline
Add the .input_enclosed wrapper to make the appearance of a self-contained input and button.
.input_enclosed
Add \.-line to the .input_enclosed wrapper to remove the background and outline and add a simple border along the bottom.
\.-line