changing a Javascript image on event listener click

i have a Div holding an image with the id sunset that i want to add an onclick to to change its width from the CSS 25% to 100%

cannot see why my code is not working

var content = document.getElementById("sunset");
var first_click = true;

content.addEventListener("click", function () {
    if (first_click) {
        content.style.width = "100%";
    }

    else {
        content.style.width = "25%";
    }

});

CSS

#sunset{
    width:25%
}