body {
    font-family: 'Inter', Arial, sans-serif;
    margin: 0;
    padding: 0;
    background: linear-gradient(135deg, #e0eafc, #cfdef3);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    overflow: auto;
}

.container {
    background: #fff;
    padding: 30px;
    border-radius: 16px;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.15), 0 4px 12px rgba(0, 0, 0, 0.1);
    max-width: 600px;
    width: 90%;
    text-align: center;
    transform: translateY(0);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.container:hover {
    transform: translateY(-5px);
    box-shadow: 0 12px 32px rgba(0, 0, 0, 0.2), 0 6px 16px rgba(0, 0, 0, 0.15);
}

header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 20px;
}

.back-btn {
    text-decoration: none;
    color: #3b82f6;
    font-weight: 600;
    font-size: 18px;
    transition: color 0.2s ease;
}

.back-btn:hover {
    color: #1d4ed8;
}

h1 {
    font-size: 28px;
    margin: 0;
    color: #1f2937;
    font-weight: 700;
}

p {
    color: #4b5563;
    font-size: 16px;
    margin: 10px 0;
}

.disclaimer {
    color: #6b7280;
    font-size: 14px;
    font-style: italic;
}

.drop-zone {
    border: 2px dashed #93c5fd;
    background: #f8fafc;
    padding: 20px;
    margin: 20px 0;
    border-radius: 12px;
    cursor: pointer;
    transition: background 0.2s ease, border-color 0.2s ease;
}

.drop-zone.dragover {
    background: #dbeafe;
    border-color: #3b82f6;
}

.drop-zone input {
    width: 100%;
    padding: 12px;
    border: 1px solid #d1d5db;
    border-radius: 8px;
    font-size: 16px;
    background: #fff;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.05);
    transition: border-color 0.2s ease;
}

.drop-zone input:focus {
    outline: none;
    border-color: #3b82f6;
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.progress {
    margin: 20px 0;
    display: flex;
    align-items: center;
    gap: 10px;
}

.spinner {
    width: 24px;
    height: 24px;
    border: 3px solid #3b82f6;
    border-top: 3px solid transparent;
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

progress {
    width: 100%;
    height: 8px;
    border-radius: 4px;
    background: #e5e7eb;
}

progress::-webkit-progress-bar {
    background: #e5e7eb;
    border-radius: 4px;
}

progress::-webkit-progress-value {
    background: #3b82f6;
    border-radius: 4px;
}

.convert-btn {
    background: linear-gradient(135deg, #3b82f6, #1d4ed8);
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 16px;
    font-weight: 600;
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.convert-btn:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(59, 130, 246, 0.4);
}

.convert-btn:disabled {
    background: #9ca3af;
    cursor: not-allowed;
    box-shadow: none;
}

.back-link {
    display: inline-block;
    margin: 20px 0;
    color: #3b82f6;
    text-decoration: none;
    font-weight: 600;
    font-size: 16px;
    transition: color 0.2s ease;
}

.back-link:hover {
    color: #1d4ed8;
}

.status {
    color: #4b5563;
    font-size: 14px;
}

.hidden {
    display: none;
}

@media (max-width: 600px) {
    .container {
        margin: 15px;
        padding: 20px;
    }

    h1 {
        font-size: 24px;
    }

    .convert-btn {
        width: 100%;
        padding: 12px;
    }

    .back-btn, .back-link {
        font-size: 16px;
    }
}