:root {
    --primary-color: #1a1a1a;
    --secondary-color: #2c2c2c;
    --accent-color: #00aaff;
    --text-color: #ffffff;
    --shadow-color: rgba(0, 0, 0, 0.5);
}

body {
    font-family: 'Roboto', sans-serif;
    background-color: var(--primary-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    background-image: radial-gradient(circle, var(--secondary-color) 1px, transparent 1px);
    background-size: 10px 10px;
}

.app-container {
    background-color: var(--secondary-color);
    padding: 30px;
    border-radius: 20px;
    box-shadow: 0 10px 30px var(--shadow-color);
    width: 90%;
    max-width: 500px;
}

.tabs {
    display: flex;
    justify-content: center;
    margin-bottom: 20px;
}

.tab-link {
    background: none;
    border: none;
    color: var(--text-color);
    font-size: 18px;
    padding: 10px 20px;
    cursor: pointer;
    transition: color 0.3s, border-bottom 0.3s;
    border-bottom: 2px solid transparent;
}

.tab-link.active {
    color: var(--accent-color);
    border-bottom: 2px solid var(--accent-color);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

.timer-display, .stopwatch-display {
    font-size: 4em;
    font-weight: 300;
    text-align: center;
    margin: 20px 0;
    letter-spacing: 2px;
}

.timer-display input {
    width: 80px;
    font-size: 1em;
    background: none;
    border: none;
    color: var(--text-color);
    text-align: center;
}

.timer-controls, .stopwatch-controls {
    display: flex;
    justify-content: center;
    gap: 15px;
}

button {
    background-color: var(--accent-color);
    color: var(--text-color);
    border: none;
    padding: 12px 25px;
    font-size: 16px;
    border-radius: 25px;
    cursor: pointer;
    transition: background-color 0.3s, box-shadow 0.3s;
    box-shadow: 0 4px 15px rgba(0, 170, 255, 0.2);
}

button:hover {
    background-color: #0088cc;
    box-shadow: 0 6px 20px rgba(0, 170, 255, 0.4);
}

@media (max-width: 480px) {
    .timer-display, .stopwatch-display {
        font-size: 3em;
    }

    .timer-display input {
        width: 60px;
    }
}