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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
    color: #333;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    background: white;
    border-radius: 20px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
    overflow: hidden;
}

header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 40px 30px;
    text-align: center;
}

header h1 {
    font-size: 2.5em;
    margin-bottom: 10px;
    font-weight: 700;
}

.subtitle {
    font-size: 1.1em;
    opacity: 0.95;
}

main {
    padding: 40px 30px;
}

.upload-section {
    margin-bottom: 30px;
}

.upload-area {
    border: 3px dashed #667eea;
    border-radius: 15px;
    padding: 60px 20px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    background: #f8f9ff;
}

.upload-area:hover {
    border-color: #764ba2;
    background: #f0f2ff;
    transform: translateY(-2px);
}

.upload-area.dragover {
    border-color: #764ba2;
    background: #e8ebff;
    transform: scale(1.02);
}

.upload-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto 20px;
    color: #667eea;
}

.upload-text {
    font-size: 1.2em;
    font-weight: 600;
    color: #667eea;
    margin-bottom: 5px;
}

.upload-subtext {
    font-size: 0.9em;
    color: #888;
}

.file-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px;
    background: #f8f9ff;
    border-radius: 15px;
    margin-top: 20px;
}

.file-details {
    display: flex;
    flex-direction: column;
    gap: 5px;
}

.file-name {
    font-weight: 600;
    color: #333;
    font-size: 1.1em;
}

.file-size {
    color: #666;
    font-size: 0.9em;
}

.btn-remove {
    background: #ff6b6b;
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 8px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.3s ease;
}

.btn-remove:hover {
    background: #ff5252;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(255, 107, 107, 0.4);
}

.split-options {
    margin-top: 30px;
}

.split-options h2 {
    margin-bottom: 20px;
    color: #333;
    font-size: 1.8em;
}

.option-tabs {
    display: flex;
    gap: 10px;
    margin-bottom: 25px;
    border-bottom: 2px solid #e0e0e0;
}

.tab-btn {
    background: none;
    border: none;
    padding: 12px 24px;
    font-size: 1em;
    font-weight: 600;
    color: #666;
    cursor: pointer;
    border-bottom: 3px solid transparent;
    transition: all 0.3s ease;
    position: relative;
    top: 2px;
}

.tab-btn:hover {
    color: #667eea;
}

.tab-btn.active {
    color: #667eea;
    border-bottom-color: #667eea;
}

.tab-content {
    display: none;
}

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

.option-group {
    margin-bottom: 25px;
}

.option-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: #333;
    font-size: 1em;
}

.select-input,
.number-input,
.text-input {
    width: 100%;
    padding: 12px 15px;
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    font-size: 1em;
    transition: all 0.3s ease;
    font-family: inherit;
}

.select-input:focus,
.number-input:focus,
.text-input:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.size-input-group {
    display: flex;
    gap: 10px;
}

.size-input-group .number-input {
    flex: 1;
}

.size-input-group .select-input {
    width: 100px;
}

.info-text {
    display: block;
    margin-top: 8px;
    font-size: 0.85em;
    color: #666;
    font-style: italic;
}

.action-buttons {
    display: flex;
    gap: 15px;
    margin-top: 30px;
}

.btn-primary,
.btn-secondary {
    padding: 14px 30px;
    border: none;
    border-radius: 8px;
    font-size: 1em;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    font-family: inherit;
}

.btn-primary {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    flex: 1;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.4);
}

.btn-primary:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.btn-secondary {
    background: #f0f0f0;
    color: #333;
}

.btn-secondary:hover {
    background: #e0e0e0;
    transform: translateY(-2px);
}

.results-section {
    margin-top: 30px;
    padding: 25px;
    background: #f8f9ff;
    border-radius: 15px;
}

.results-section h2 {
    margin-bottom: 20px;
    color: #333;
    font-size: 1.8em;
}

.results-info {
    margin-bottom: 20px;
    padding: 15px;
    background: white;
    border-radius: 8px;
    color: #333;
}

.download-buttons {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 15px;
    margin-bottom: 20px;
}

.download-btn {
    background: #667eea;
    color: white;
    border: none;
    padding: 12px 20px;
    border-radius: 8px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.3s ease;
    text-align: center;
}

.download-btn:hover {
    background: #764ba2;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
}

#downloadAllBtn {
    width: 100%;
    margin-top: 15px;
}

.loading {
    text-align: center;
    padding: 40px;
}

.spinner {
    border: 4px solid #f3f3f3;
    border-top: 4px solid #667eea;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    animation: spin 1s linear infinite;
    margin: 0 auto 20px;
}

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

.loading p {
    color: #667eea;
    font-weight: 600;
    font-size: 1.1em;
}

@media (max-width: 768px) {
    header h1 {
        font-size: 2em;
    }

    main {
        padding: 30px 20px;
    }

    .action-buttons {
        flex-direction: column;
    }

    .download-buttons {
        grid-template-columns: 1fr;
    }
}