let seconds;
    let timer;
    let isRunning = false;
function start(){
        isRunning = !isRunning;
        if(isRunning == true) {
        seconds = document.getElementById("input").value;
        document.getElementById('count-down').innerHTML = seconds;
        timer = setInterval(check, 1000);
        } else {
            pause();
        }
    };
    function pause () {
        clearInterval(timer);
        timer = null;
    }
function check() {
    if(seconds <= 0 ) {
        clearInterval(timer);
        document.getElementById('body').style.backgroundColor = "#80bfff";
    } else {
        seconds--;
        document.getElementById('count-down').innerHTML = seconds;
    }
};
</script>
    <div id = "timer">
        <div id="header">
            <p>Timer</p>
        </div>
        <div id="body">
            <p id="count-down"></p>
            <p class="inline">Enter time(in seconds)</p>
            <input class="inline" type="text" id="input">
            <button type="button" onclick="start()">Start</button>
        </div>
    </div>