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

:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --info: #3b82f6;
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --border: #334155;
    --shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
    --radius: 16px;
    --radius-sm: 8px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    font-family: 'Inter', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    overflow-x: hidden;
}

/* Animated Background */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: 
        radial-gradient(ellipse at 20% 20%, rgba(99, 102, 241, 0.15) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 80%, rgba(16, 185, 129, 0.1) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 50%, rgba(59, 130, 246, 0.05) 0%, transparent 70%);
    pointer-events: none;
    z-index: -1;
}

.app-container {
    display: flex;
    min-height: 100vh;
    max-width: 1600px;
    margin: 0 auto;
}

/* Sidebar */
.sidebar {
    width: 280px;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border);
    padding: 24px;
    display: flex;
    flex-direction: column;
    position: fixed;
    height: 100vh;
    overflow-y: auto;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 32px;
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
}

.logo-icon svg {
    width: 24px;
    height: 24px;
    color: white;
}

.logo span {
    font-size: 22px;
    font-weight: 700;
    background: linear-gradient(135deg, var(--text-primary), var(--primary-light));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-menu {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-bottom: 32px;
}

.nav-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-size: 14px;
    font-weight: 500;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
    width: 100%;
    text-align: left;
}

.nav-item svg {
    width: 20px;
    height: 20px;
}

.nav-item:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.nav-item.active {
    background: var(--primary);
    color: white;
}

.badge {
    margin-left: auto;
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    font-size: 12px;
    padding: 2px 8px;
    border-radius: 999px;
    font-weight: 600;
}

.nav-item.active .badge {
    background: rgba(255, 255, 255, 0.2);
    color: white;
}

/* Progress Section */
.progress-section {
    margin-top: auto;
    padding-top: 24px;
    border-top: 1px solid var(--border);
}

.progress-section h3 {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 16px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.progress-ring {
    position: relative;
    width: 120px;
    height: 120px;
    margin: 0 auto 16px;
}

.progress-ring svg {
    transform: rotate(-90deg);
    width: 100%;
    height: 100%;
}

.progress-ring-bg {
    fill: none;
    stroke: var(--bg-tertiary);
    stroke-width: 8;
}

.progress-ring-fill {
    fill: none;
    stroke: url(#progressGradient);
    stroke-width: 8;
    stroke-linecap: round;
    stroke-dasharray: 283;
    stroke-dashoffset: 283;
    transition: stroke-dashoffset 0.5s ease;
}

.progress-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
}

.progress-text span {
    display: block;
    font-size: 24px;
    font-weight: 700;
    color: var(--text-primary);
}

.progress-text small {
    font-size: 12px;
    color: var(--text-secondary);
}

.progress-message {
    text-align: center;
    font-size: 13px;
    color: var(--text-secondary);
}

/* Main Content */
.main-content {
    flex: 1;
    margin-left: 280px;
    padding: 32px 40px;
    max-width: calc(100% - 280px);
}

.header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 32px;
}

.header-left h1 {
    font-size: 32px;
    font-weight: 700;
    margin-bottom: 8px;
}

.header-left p {
    color: var(--text-secondary);
    font-size: 14px;
}

.stats {
    display: flex;
    gap: 24px;
}

.stat {
    text-align: center;
    padding: 16px 24px;
    background: var(--bg-secondary);
    border-radius: var(--radius);
    border: 1px solid var(--border);
    min-width: 80px;
}

.stat-value {
    display: block;
    font-size: 28px;
    font-weight: 700;
    color: var(--primary);
}

.stat-label {
    font-size: 12px;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Add Task Section */
.add-task-section {
    margin-bottom: 24px;
}

.add-task-container {
    display: flex;
    gap: 12px;
    background: var(--bg-secondary);
    padding: 16px;
    border-radius: var(--radius);
    border: 1px solid var(--border);
    box-shadow: var(--shadow);
}

#task-input {
    flex: 1;
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 12px 16px;
    color: var(--text-primary);
    font-size: 15px;
    font-family: inherit;
    outline: none;
    transition: var(--transition);
}

#task-input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

#task-input::placeholder {
    color: var(--text-muted);
}

#priority-select {
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 12px 16px;
    color: var(--text-primary);
    font-size: 14px;
    font-family: inherit;
    cursor: pointer;
    outline: none;
    min-width: 140px;
}

#priority-select:focus {
    border-color: var(--primary);
}

.btn-primary {
    display: flex;
    align-items: center;
    gap: 8px;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 25px -5px rgba(99, 102, 241, 0.4);
}

.btn-primary svg {
    width: 18px;
    height: 18px;
}

/* Task List */
.task-filters {
    display: flex;
    gap: 8px;
    margin-bottom: 16px;
}

.filter-btn {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    color: var(--text-secondary);
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
}

.filter-btn:hover {
    color: var(--text-primary);
    border-color: var(--primary);
}

.filter-btn.active {
    background: var(--primary);
    border-color: var(--primary);
    color: white;
}

.task-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.task-item {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 16px 20px;
    display: flex;
    align-items: center;
    gap: 16px;
    transition: var(--transition);
    animation: slideIn 0.3s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(-20px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.task-item:hover {
    border-color: var(--primary);
    transform: translateX(4px);
}

.task-item.completed {
    opacity: 0.6;
}

.task-item.completed .task-text {
    text-decoration: line-through;
    color: var(--text-muted);
}

.task-checkbox {
    width: 22px;
    height: 22px;
    border: 2px solid var(--border);
    border-radius: 6px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
    flex-shrink: 0;
}

.task-checkbox:hover {
    border-color: var(--primary);
}

.task-checkbox.checked {
    background: var(--success);
    border-color: var(--success);
}

.task-checkbox.checked svg {
    width: 14px;
    height: 14px;
    color: white;
}

.task-content {
    flex: 1;
    min-width: 0;
}

.task-text {
    font-size: 15px;
    font-weight: 500;
    margin-bottom: 4px;
    word-break: break-word;
}

.task-meta {
    display: flex;
    align-items: center;
    gap: 12px;
}

.priority-badge {
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    padding: 3px 10px;
    border-radius: 999px;
    letter-spacing: 0.3px;
}

.priority-badge.low {
    background: rgba(16, 185, 129, 0.15);
    color: var(--success);
}

.priority-badge.medium {
    background: rgba(245, 158, 11, 0.15);
    color: var(--warning);
}

.priority-badge.high {
    background: rgba(239, 68, 68, 0.15);
    color: var(--danger);
}

.task-date {
    font-size: 12px;
    color: var(--text-muted);
}

.task-actions {
    display: flex;
    gap: 8px;
    opacity: 0;
    transition: var(--transition);
}

.task-item:hover .task-actions {
    opacity: 1;
}

.task-btn {
    width: 32px;
    height: 32px;
    border: none;
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    border-radius: 6px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.task-btn:hover {
    background: var(--primary);
    color: white;
}

.task-btn.delete:hover {
    background: var(--danger);
}

.task-btn svg {
    width: 16px;
    height: 16px;
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: 60px 20px;
    display: none;
}

.empty-state.show {
    display: block;
}

.empty-icon {
    width: 80px;
    height: 80px;
    background: var(--bg-secondary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 24px;
}

.empty-icon svg {
    width: 40px;
    height: 40px;
    color: var(--primary);
}

.empty-state h3 {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 8px;
}

.empty-state p {
    color: var(--text-secondary);
    font-size: 14px;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(15, 23, 42, 0.8);
    backdrop-filter: blur(8px);
    z-index: 1000;
    align-items: center;
    justify-content: center;
}

.modal.show {
    display: flex;
}

.modal-content {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 32px;
    width: 90%;
    max-width: 450px;
    animation: modalIn 0.3s ease;
}

@keyframes modalIn {
    from {
        opacity: 0;
        transform: scale(0.9);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

.modal-content h2 {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 20px;
}

.modal-content input,
.modal-content select {
    width: 100%;
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 12px 16px;
    color: var(--text-primary);
    font-size: 15px;
    font-family: inherit;
    margin-bottom: 16px;
    outline: none;
}

.modal-content input:focus,
.modal-content select:focus {
    border-color: var(--primary);
}

.modal-actions {
    display: flex;
    gap: 12px;
    justify-content: flex-end;
}

.btn-secondary {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border: none;
    padding: 10px 20px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
}

.btn-secondary:hover {
    background: var(--border);
}

/* SVG Gradient Definition */
svg defs {
    position: absolute;
}

/* Responsive */
@media (max-width: 1024px) {
    .sidebar {
        width: 240px;
    }
    
    .main-content {
        margin-left: 240px;
        max-width: calc(100% - 240px);
        padding: 24px;
    }
}

@media (max-width: 768px) {
    .sidebar {
        width: 100%;
        position: relative;
        height: auto;
        border-right: none;
        border-bottom: 1px solid var(--border);
    }
    
    .main-content {
        margin-left: 0;
        max-width: 100%;
    }
    
    .app-container {
        flex-direction: column;
    }
    
    .header {
        flex-direction: column;
        gap: 16px;
    }
    
    .stats {
        width: 100%;
        justify-content: space-around;
    }
    
    .add-task-container {
        flex-direction: column;
    }
    
    .progress-section {
        display: none;
    }
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--bg-tertiary);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--border);
}