/* ===========================
   CSS Variables & Theme
   =========================== */
:root {
    /* Light Theme Colors */
    --bg-primary: #f5f5f5;
    --bg-secondary: #ffffff;
    --bg-tertiary: #fafafa;
    --text-primary: #2d3748;
    --text-secondary: #4a5568;
    --text-muted: #718096;
    --border-color: #e2e8f0;

    /* Session Colors */
    --focus-color: #e74c3c;
    --short-break-color: #3498db;
    --long-break-color: #2ecc71;

    /* UI Colors */
    --primary-color: #e74c3c;
    --secondary-color: #718096;
    --danger-color: #e74c3c;
    --success-color: #2ecc71;
    --warning-color: #f39c12;

    /* Category Colors */
    --work-color: #3498db;
    --learning-color: #9b59b6;

    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.15);

    /* Transitions */
    --transition: all 0.3s ease;
}

[data-theme="dark"] {
    --bg-primary: #1a202c;
    --bg-secondary: #2d3748;
    --bg-tertiary: #374151;
    --text-primary: #f7fafc;
    --text-secondary: #e2e8f0;
    --text-muted: #a0aec0;
    --border-color: #4a5568;

    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.4);
}

/* ===========================
   Global Styles
   =========================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: var(--transition);
}

.app-container {
    min-height: 100vh;
    padding-bottom: 2rem;
}

/* ===========================
   Header
   =========================== */
.header {
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow-sm);
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.header-controls {
    display: flex;
    gap: 0.5rem;
}

.theme-toggle,
.settings-btn {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.5rem 0.75rem;
    font-size: 1.25rem;
    cursor: pointer;
    transition: var(--transition);
}

.theme-toggle:hover,
.settings-btn:hover {
    background: var(--border-color);
    transform: translateY(-2px);
}

/* ===========================
   Main Content
   =========================== */
.main-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
}

/* ===========================
   Timer Section
   =========================== */
.timer-section {
    background: var(--bg-secondary);
    border-radius: 16px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow-md);
    text-align: center;
}

.session-tabs {
    display: flex;
    justify-content: center;
    gap: 0.5rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.session-tab {
    background: var(--bg-tertiary);
    border: 2px solid transparent;
    border-radius: 8px;
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-secondary);
    cursor: pointer;
    transition: var(--transition);
}

.session-tab:hover {
    background: var(--border-color);
}

.session-tab.active {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.session-tab.active[data-session="shortBreak"] {
    background: var(--short-break-color);
    border-color: var(--short-break-color);
}

.session-tab.active[data-session="longBreak"] {
    background: var(--long-break-color);
    border-color: var(--long-break-color);
}

/* Timer Display with Circular Progress */
.timer-display {
    position: relative;
    display: inline-block;
    margin: 2rem 0;
}

.progress-ring {
    transform: rotate(-90deg);
}

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

.progress-ring-circle {
    fill: none;
    stroke: var(--primary-color);
    stroke-width: 8;
    stroke-linecap: round;
    stroke-dasharray: 848;
    stroke-dashoffset: 848;
    transition: stroke-dashoffset 1s linear, stroke 0.3s ease;
}

.timer-content {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
    width: 100%;
}

.timer-text {
    font-size: 4rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    font-variant-numeric: tabular-nums;
}

.session-info {
    font-size: 1rem;
    color: var(--text-muted);
    margin-bottom: 0.5rem;
}

.active-task {
    font-size: 0.875rem;
    color: var(--primary-color);
    font-weight: 600;
    max-width: 200px;
    margin: 0 auto;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

/* Timer Controls */
.timer-controls {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.keyboard-hints {
    display: flex;
    justify-content: center;
    gap: 2rem;
    font-size: 0.875rem;
    color: var(--text-muted);
    margin-top: 1rem;
}

/* ===========================
   Stats Section
   =========================== */
.stats-section {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
}

.stat-card {
    background: var(--bg-secondary);
    border-radius: 12px;
    padding: 1.5rem;
    text-align: center;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.stat-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.stat-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-muted);
}

/* ===========================
   Tasks Section
   =========================== */
.tasks-section {
    background: var(--bg-secondary);
    border-radius: 16px;
    padding: 2rem;
    box-shadow: var(--shadow-md);
}

.tasks-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.tasks-header h2 {
    font-size: 1.5rem;
    color: var(--text-primary);
}

.task-filters {
    display: flex;
    gap: 0.5rem;
}

.filter-btn {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
    cursor: pointer;
    transition: var(--transition);
}

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

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

/* Add Task Form */
.add-task-form {
    background: var(--bg-tertiary);
    border-radius: 12px;
    padding: 1.5rem;
    margin-bottom: 2rem;
}

.add-task-form input[type="text"],
.add-task-form textarea {
    width: 100%;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.75rem;
    font-size: 1rem;
    color: var(--text-primary);
    margin-bottom: 1rem;
    font-family: inherit;
    transition: var(--transition);
}

.add-task-form input[type="text"]:focus,
.add-task-form textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

.add-task-form textarea {
    resize: vertical;
    min-height: 80px;
}

.task-form-controls {
    display: flex;
    gap: 1rem;
    align-items: center;
    flex-wrap: wrap;
}

.category-select {
    flex: 1;
    min-width: 120px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.75rem;
    font-size: 1rem;
    color: var(--text-primary);
    cursor: pointer;
}

.task-form-controls input[type="number"],
.task-form-controls input[type="text"].project-input {
    flex: 1;
    min-width: 120px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.75rem;
    font-size: 1rem;
    color: var(--text-primary);
}

/* Task List */
.task-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.task-card {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.25rem;
    transition: var(--transition);
    animation: slideIn 0.3s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.task-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

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

.task-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 0.75rem;
    gap: 1rem;
}

.task-title-group {
    flex: 1;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.task-checkbox {
    width: 20px;
    height: 20px;
    cursor: pointer;
    accent-color: var(--success-color);
}

.task-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    flex: 1;
}

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

.category-badge {
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
}

.category-badge.work {
    background: rgba(52, 152, 219, 0.2);
    color: var(--work-color);
}

.category-badge.learning {
    background: rgba(155, 89, 182, 0.2);
    color: var(--learning-color);
}

.project-badge {
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 600;
    background: rgba(243, 156, 18, 0.2);
    color: var(--warning-color);
    margin-left: 0.5rem;
}

.task-badges {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.task-description {
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-bottom: 1rem;
    line-height: 1.5;
}

.task-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.task-pomodoros {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-muted);
    font-size: 0.875rem;
}

.pomodoro-count {
    font-weight: 600;
    color: var(--primary-color);
}

.task-actions {
    display: flex;
    gap: 0.5rem;
}

.task-actions button {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

.empty-state {
    text-align: center;
    padding: 3rem 1rem;
    color: var(--text-muted);
}

.empty-state.hidden {
    display: none;
}

/* ===========================
   Buttons
   =========================== */
.btn {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
}

.btn:active {
    transform: translateY(0);
}

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

.btn-primary:hover {
    background: #c0392b;
    border-color: #c0392b;
}

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

.btn-secondary:hover {
    background: #5a6c7d;
}

.btn-danger {
    background: var(--danger-color);
    color: white;
    border-color: var(--danger-color);
}

.btn-danger:hover {
    background: #c0392b;
}

.btn-large {
    padding: 1rem 3rem;
    font-size: 1.25rem;
}

/* ===========================
   Modal
   =========================== */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

.modal.active {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 1rem;
}

.modal-content {
    background: var(--bg-secondary);
    border-radius: 16px;
    max-width: 600px;
    width: 100%;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
    animation: slideUp 0.3s ease;
}

@keyframes slideUp {
    from {
        transform: translateY(50px);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.modal-header h2 {
    font-size: 1.5rem;
    color: var(--text-primary);
}

.modal-close {
    background: none;
    border: none;
    font-size: 2rem;
    color: var(--text-muted);
    cursor: pointer;
    line-height: 1;
    transition: var(--transition);
}

.modal-close:hover {
    color: var(--text-primary);
}

.modal-body {
    padding: 1.5rem;
}

/* Settings Sections */
.settings-section {
    margin-bottom: 2rem;
}

.settings-section h3 {
    font-size: 1.125rem;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.setting-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 0;
    gap: 1rem;
}

.setting-item label {
    color: var(--text-secondary);
    flex: 1;
}

.setting-item input[type="number"],
.setting-item input[type="range"],
.setting-item select,
.setting-item textarea,
.setting-item input[type="text"] {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.5rem;
    color: var(--text-primary);
    font-family: inherit;
}

.setting-item input[type="number"],
.setting-item select {
    width: 100px;
}

.setting-item input[type="range"] {
    width: 150px;
}

.setting-item input[type="checkbox"] {
    width: 20px;
    height: 20px;
    cursor: pointer;
    accent-color: var(--primary-color);
}

.setting-item textarea {
    width: 100%;
    min-height: 80px;
    resize: vertical;
}

.setting-item input[type="text"] {
    flex: 1;
}

.settings-section button {
    margin-right: 0.5rem;
    margin-bottom: 0.5rem;
}

/* ===========================
   Responsive Design
   =========================== */
@media (max-width: 768px) {
    .header-content {
        padding: 0 1rem;
    }

    .main-content {
        padding: 1rem;
    }

    .timer-section {
        padding: 1.5rem 1rem;
    }

    .timer-text {
        font-size: 3rem;
    }

    .progress-ring {
        width: 250px;
        height: 250px;
    }

    .progress-ring circle {
        cx: 125;
        cy: 125;
        r: 110;
    }

    .tasks-header {
        flex-direction: column;
        align-items: flex-start;
    }

    .task-form-controls {
        flex-direction: column;
    }

    .task-form-controls > * {
        width: 100%;
    }

    .keyboard-hints {
        flex-direction: column;
        gap: 0.5rem;
    }

    .setting-item {
        flex-direction: column;
        align-items: flex-start;
    }

    .setting-item input[type="number"],
    .setting-item input[type="range"],
    .setting-item select {
        width: 100%;
    }
}

@media (max-width: 480px) {
    .timer-text {
        font-size: 2.5rem;
    }

    .progress-ring {
        width: 200px;
        height: 200px;
    }

    .progress-ring circle {
        cx: 100;
        cy: 100;
        r: 85;
    }

    .session-tabs {
        flex-direction: column;
    }

    .session-tab {
        width: 100%;
    }
}

/* ===========================
   Footer
   =========================== */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: 2rem 0;
    margin-top: 3rem;
    text-align: center;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

.footer-note {
    color: var(--text-muted);
    font-size: 0.813rem;
    margin: 0 0 0.75rem 0;
    line-height: 1.5;
}

.footer-credit {
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin: 0 0 0.5rem 0;
}

.footer-opensource {
    color: var(--text-muted);
    font-size: 0.813rem;
    margin: 0;
}

.footer-link {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition);
}

.footer-link:hover {
    color: var(--text-primary);
    text-decoration: underline;
}

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

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

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

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

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