* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: "Poppins", sans-serif;
}

html,
body {
    height: 100%;
}

body {
    width: 100%;
    height: 100%;
    background: linear-gradient(to left top, #0045d6, #00a9f6);
}

header {
    width: 100%;
    height: 13vh;
    background-color: #fff;
    color: #0045d6;
    text-transform: uppercase;
    display: flex;
    justify-content: center;
    align-items: center;
}

.content {
    width: 100%;
    height: 60vh;
    font-size: 3rem;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
}

.content #seconds {
    width: 250px;
    font-size: 2rem;
    padding: 1rem;
    outline: none;
    background: none;
    border: none;
    border-bottom: 3px solid #fff;
    color: #fff;
    margin-bottom: 2rem;
}

#seconds::placeholder {
    color: #ddd;
    font-size: 1.7rem;
}

.btn {
    background-color: #fff;
    border-radius: 4px;
    border: none;
    outline: none;
    cursor: pointer;
    padding: 0.8rem 1.7rem;
    font-size: 1.2rem;
    font-weight: 700;
}

.start {
    color: #1f0;
}

.stop {
    color: #e00;
}

#start,
#stop,
#continue {
    display: none;
}

.counter {
    color: #fff;
}