:root {
    --bg-color: #f8fafc;
    --sidebar-bg: #ffffff;
    --text-primary: #0f172a;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    --accent: #2563eb;
    --accent-hover: #1d4ed8;
    --accent-light: #eff6ff;
    --border-color: #e2e8f0;
    --success: #10b981;
    --success-hover: #059669;
    --danger: #ef4444;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    height: 100vh;
    width: 100vw;
    overflow: hidden;
}

.app-container {
    display: flex;
    height: 100%;
    width: 100%;
}

/* === Sidebar === */
.sidebar {
    width: 280px;
    background-color: var(--sidebar-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    padding-top: 2rem;
    padding-bottom: 2rem;
    flex-shrink: 0;
    z-index: 10;
    overflow: hidden;
}

.logo {
    margin-bottom: 2rem;
    padding: 0 1.5rem;
    flex-shrink: 0;
}

.logo h1 {
    font-size: 1.75rem;
    font-weight: 800;
    letter-spacing: -0.025em;
    color: var(--text-primary);
}

.highlight {
    color: var(--accent);
}

.nav-section {
    flex: 1;
    overflow-y: auto;
    padding: 0 1.5rem;
}

/* Custom Scrollbar */
.nav-section::-webkit-scrollbar, .main-content::-webkit-scrollbar {
    width: 5px;
}
.nav-section::-webkit-scrollbar-track, .main-content::-webkit-scrollbar-track {
    background: transparent;
}
.nav-section::-webkit-scrollbar-thumb, .main-content::-webkit-scrollbar-thumb {
    background: #cbd5e1;
    border-radius: 10px;
}
.nav-section::-webkit-scrollbar-thumb:hover, .main-content::-webkit-scrollbar-thumb:hover {
    background: #94a3b8;
}

.nav-title {
    font-size: 0.725rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-weight: 700;
    color: var(--text-light);
    margin: 1.5rem 0 0.5rem 0.5rem;
}

.tool-list {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.tool-btn {
    display: flex;
    align-items: center;
    width: 100%;
    background: transparent;
    border: none;
    padding: 0.65rem 0.75rem;
    border-radius: 0.5rem;
    color: var(--text-secondary);
    font-size: 0.95rem;
    font-weight: 500;
    text-align: left;
    cursor: pointer;
    transition: all 0.2s ease;
    gap: 0.75rem;
}

.tool-btn .icon {
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-light);
    transition: color 0.2s ease;
}

.tool-btn:hover {
    background-color: #f1f5f9;
    color: var(--text-primary);
}

.tool-btn:hover .icon {
    color: var(--accent);
}

.tool-btn.active {
    background-color: var(--accent-light);
    color: var(--accent);
    font-weight: 600;
}

.tool-btn.active .icon {
    color: var(--accent);
}

/* === Main Content === */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    background-color: var(--bg-color);
    overflow-y: auto;
}

.top-bar {
    padding: 3rem 4rem 1.5rem 4rem;
}

.top-bar h2 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.top-bar p {
    color: var(--text-secondary);
    font-size: 1.05rem;
}

.workspace-wrapper {
    padding: 0 4rem 4rem 4rem;
    flex: 1;
    display: flex;
    flex-direction: column;
}

.workspace {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    padding: 3rem;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
    max-width: 800px;
    width: 100%;
}

/* === Dropzone === */
.file-upload {
    border: 2px dashed #cbd5e1;
    border-radius: 0.75rem;
    padding: 4rem 2rem;
    text-align: center;
    cursor: pointer;
    background-color: #f8fafc;
    transition: all 0.2s ease;
    margin-bottom: 1.5rem;
}

.upload-icon {
    color: #94a3b8;
    margin-bottom: 1rem;
    transition: color 0.2s;
}

.file-upload h3 {
    font-size: 1.15rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.file-upload p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: 1.5rem;
}

.browse-btn {
    display: inline-block;
    background: white;
    border: 1px solid var(--border-color);
    padding: 0.5rem 1.5rem;
    border-radius: 2rem;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-primary);
    box-shadow: 0 1px 2px rgba(0,0,0,0.05);
    transition: all 0.2s;
}

.file-upload:hover, .file-upload.dragover {
    border-color: var(--accent);
    background-color: var(--accent-light);
}

.file-upload:hover .upload-icon, .file-upload.dragover .upload-icon {
    color: var(--accent);
}

.file-upload:hover .browse-btn {
    border-color: var(--accent);
    color: var(--accent);
}

/* === File Info === */
#file-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: #f8fafc;
    padding: 1rem 1.5rem;
    border-radius: 0.5rem;
    border: 1px solid var(--border-color);
    margin-bottom: 1.5rem;
}

.file-details {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

#file-name {
    font-weight: 500;
    color: var(--text-primary);
}

#remove-file {
    background: transparent;
    border: none;
    color: var(--text-light);
    cursor: pointer;
    transition: color 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
}

#remove-file:hover {
    color: var(--danger);
}

/* === Action Button === */
.action-area {
    display: flex;
    justify-content: flex-end;
}

button#convert-btn {
    background: var(--accent);
    color: white;
    border: none;
    padding: 0.85rem 2.5rem;
    border-radius: 0.5rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow: 0 4px 6px -1px rgba(37, 99, 235, 0.2);
}

button#convert-btn:hover:not(:disabled) {
    background: var(--accent-hover);
    transform: translateY(-1px);
    box-shadow: 0 6px 8px -1px rgba(37, 99, 235, 0.3);
}

button#convert-btn:disabled {
    background: #cbd5e1;
    color: white;
    cursor: not-allowed;
    box-shadow: none;
}

/* === States === */
.hidden {
    display: none !important;
}

#loading {
    text-align: center;
    padding: 3rem 0;
}

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid #e2e8f0;
    border-top-color: var(--accent);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
    margin: 0 auto 1.5rem;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

#loading p {
    color: var(--text-secondary);
    font-weight: 500;
}

#result {
    text-align: center;
    padding: 2rem 0;
}

.success-icon {
    margin-bottom: 1rem;
}

#result h3 {
    font-size: 1.5rem;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

#result p {
    color: var(--text-secondary);
    margin-bottom: 2rem;
}

#download-link {
    display: inline-block;
    background: var(--success);
    color: white;
    text-decoration: none;
    padding: 0.85rem 2.5rem;
    border-radius: 0.5rem;
    font-weight: 600;
    transition: all 0.2s ease;
    box-shadow: 0 4px 6px -1px rgba(16, 185, 129, 0.2);
}

#download-link:hover {
    background: var(--success-hover);
    transform: translateY(-1px);
    box-shadow: 0 6px 8px -1px rgba(16, 185, 129, 0.3);
}

@keyframes pulse {
    0% { opacity: 1; }
    50% { opacity: 0.5; }
    100% { opacity: 1; }
}