* { box-sizing: border-box; }
body {
    margin: 0;
    min-height: 100vh;
    display: grid;
    place-items: center;
    background: #000;
    color: #fff;
    font-family: Arial, sans-serif;
    padding: 16px;
}
.card {
    width: min(420px, 92vw);
    background: #111;
    border: 1px solid #333;
    border-radius: 18px;
    padding: 22px;
    box-shadow: 0 10px 40px rgba(0,0,0,.45);
}
h1 {
    margin: 0 0 18px;
    font-size: 28px;
}
label {
    display: block;
    margin: 12px 0 6px;
    font-size: 14px;
    opacity: .9;
}
input {
    width: 100%;
    padding: 14px 14px;
    border-radius: 12px;
    border: 1px solid #333;
    background: #1b1b1b;
    color: #fff;
    font-size: 16px;
    outline: none;
}
button {
    margin-top: 18px;
    width: 100%;
    padding: 14px;
    border: 0;
    border-radius: 12px;
    background: #00c853;
    color: #fff;
    font-weight: bold;
    font-size: 18px;
    cursor: pointer;
}
.flash {
    margin-bottom: 14px;
    padding: 12px;
    border-radius: 10px;
    background: #222;
    border: 1px solid #444;
}
.error { color: #ff7b7b; }
.success { color: #88ff9a; }