var age = document.getElementById('age');
var gender = document.getElementById('gender');
var weight = document.getElementById('weight');
var gender = document.getElementById('gender');
var btn = document.getElementById('btn');
var p1 = document.getElementById('puppy1');
var p2 = document.getElementById('puppy2');


 btn.addEventListener('click', function() {
    //alert('hello world!');
    document.getElementById('display').innerHTML += '<br>Some new content!';
});

gender.addEventListener('change', function(){
	if ( gender.value === "female") {
		p1.style.right = '500px';
		p2.style.right = '0px';
	} else {
		p1.style.right = '0px';
		p2.style.right = '500px';

	}

});