index.html


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <link rel="stylesheet" href="style.css">
    <title>timer</title>
</head>
<body>
    <header>
         
    </header>
    <main>
        <div class="back-color">
           <h1>
               Timer App
           </h1>
           <label>Enter seconds: </label>
           <input type="number" id="seconds" min="1" max="1000000" autofocus/><br/></br>
           <button type="button" id="start_btn" onclick="startTimer()">START TIMER</button>
           <button type="button" id="sop_btn" onclick="stopTimer()">STOP TIMER</button>
        </div>
    </main>
</body>
</html>