* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #1a1a1a 0%, #2d2d2d 50%, #0f0f0f 100%);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #e2e8f0;
}

.container {
    width: 100%;
    max-width: 800px;
    padding: 20px;
}

.countdown-card {
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    background: rgba(30, 30, 30, 0.95);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    padding: 40px;
    text-align: center;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.3);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

h1 {
    font-size: 2.5rem;
    color: #f7fafc;
    margin-bottom: 30px;
    font-weight: 300;
}

.time-display {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: 20px;
    margin-bottom: 40px;
}

.time-unit {
    background: linear-gradient(135deg, #2d3748, #4a5568);
    color: white;
    border-radius: 15px;
    padding: 20px;
    min-height: 120px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.4);
    transition: transform 0.3s ease;
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.time-unit:hover {
    transform: translateY(-5px);
    background: linear-gradient(135deg, #374151, #4b5563);
}

.time-value {
    font-size: 2.5rem;
    font-weight: bold;
    line-height: 1;
    margin-bottom: 5px;
}

.time-label {
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    opacity: 0.9;
}

.total-hours {
    background: linear-gradient(135deg, #365314, #4d7c0f);
    color: #ecfccb;
    border-radius: 15px;
    padding: 25px;
    margin-bottom: 30px;
    display: flex;
    flex-direction: column;
    align-items: center;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.4);
    border: 1px solid rgba(101, 163, 13, 0.3);
}

.hours-number {
    font-size: 3rem;
    font-weight: bold;
    margin-bottom: 5px;
}

.hours-label {
    font-size: 1.1rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    font-weight: 500;
}

.target-date {
    color: #a0aec0;
    font-size: 1rem;
    margin-bottom: 20px;
}

.target-date #target-datetime {
    font-weight: 600;
    color: #e2e8f0;
}

.completed-message {
    background: linear-gradient(135deg, #065f46, #047857);
    color: white;
    border-radius: 15px;
    padding: 30px;
    font-size: 1.5rem;
    font-weight: bold;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.4);
    animation: celebrate 2s ease-in-out infinite alternate;
    border: 1px solid rgba(6, 182, 212, 0.3);
}

@keyframes celebrate {
    0% { transform: scale(1); }
    100% { transform: scale(1.05); }
}

.error-message {
    background: linear-gradient(135deg, #7f1d1d, #991b1b);
    color: white;
    border-radius: 15px;
    padding: 25px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.4);
    border: 1px solid rgba(239, 68, 68, 0.3);
}

.error-message p {
    margin-bottom: 10px;
}

.error-message p:last-child {
    margin-bottom: 0;
    font-size: 0.9rem;
    opacity: 0.9;
}

/* Responsive Design */
@media (max-width: 768px) {
    .countdown-card {
        padding: 30px 20px;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    .time-display {
        grid-template-columns: repeat(2, 1fr);
        gap: 15px;
    }
    
    .time-unit {
        padding: 15px;
        min-height: 100px;
    }
    
    .time-value {
        font-size: 2rem;
    }
    
    .hours-number {
        font-size: 2.5rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 15px;
    }
    
    .countdown-card {
        padding: 25px 15px;
    }
    
    h1 {
        font-size: 1.5rem;
        margin-bottom: 25px;
    }
    
    .time-display {
        grid-template-columns: 1fr;
        gap: 10px;
    }
    
    .time-unit {
        padding: 15px;
        min-height: 80px;
    }
    
    .time-value {
        font-size: 1.8rem;
    }
    
    .time-label {
        font-size: 0.8rem;
    }
    
    .hours-number {
        font-size: 2rem;
    }
    
    .hours-label {
        font-size: 1rem;
    }
}