:root {
    --bg-primary: #ffffff;
    --bg-secondary: #f9f9f9;
    --text-main: #1a1a1a;
    --text-muted: #666666;
    --border-color: #e0e0e0;
    --accent-color: #000000;
    --accent-contrast: #ffffff;
    --card-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    --transition: all 0.3s ease;
}

[data-theme='dark'] {
    --bg-primary: #121212;
    --bg-secondary: #1e1e1e;
    --text-main: #e0e0e0;
    --text-muted: #a0a0a0;
    --border-color: #333333;
    --accent-color: #ffffff;
    --accent-contrast: #000000;
    --card-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

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

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

.container {
    max-width: 600px;
    margin: 2rem auto;
    padding: 0 1rem;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

h1 {
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: -0.02em;
}

h2 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
}

.card {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--card-shadow);
}

/* Header & Controls */
.header-controls {
    display: flex;
    gap: 0.5rem;
}

.icon-btn {
    background: none;
    border: 1px solid var(--border-color);
    padding: 0.5rem;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    transition: var(--transition);
}

.icon-btn:hover {
    background-color: var(--bg-secondary);
}

/* Statistics Dashboard */
#stats-dashboard.hidden {
    display: none !important;
}

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

.stats-header h2 {
    margin-bottom: 0;
}

.close-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-muted);
    cursor: pointer;
}

.stats-content {
    display: flex;
    align-items: center;
    gap: 2rem;
}

.chart-wrapper {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.3rem;
    flex: 0 0 100px;
}

.percentage-label {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.chart-container {
    width: 100%;
}

.circular-chart {
    display: block;
    max-width: 100%;
}

.circle-bg {
    fill: none;
    stroke: var(--border-color);
    stroke-width: 2.8;
}

.circle {
    fill: none;
    stroke: var(--accent-color);
    stroke-width: 2.8;
    stroke-linecap: round;
    transition: stroke-dasharray 0.5s ease;
}

.stats-grid {
    flex-grow: 1;
    display: grid;
    grid-template-columns: 1fr;
    gap: 1rem;
}

.stat-item {
    display: flex;
    flex-direction: column;
}

.stat-label {
    font-size: 0.8rem;
    color: var(--text-muted);
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 700;
}

/* Form Styling */
#todo-form {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.form-main-row {
    display: flex;
    flex-direction: row;
    align-items: center;
    gap: 0.75rem;
}

#habit-options {
    margin-top: 0.5rem;
    padding-top: 0.75rem;
    border-top: 1px dashed var(--border-color);
}

#habit-options.hidden {
    display: none;
}

.range-picker {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    color: var(--text-muted);
}

.range-picker label {
    font-weight: 600;
}

.range-picker input[type="date"] {
    padding: 0.3rem 0.5rem;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    background-color: var(--bg-primary);
    color: var(--text-main);
    font-size: 0.85rem;
}

/* Filter Bar */
/* Calendar Section */
#calendar-section {
    padding: 1rem;
}

.calendar-controls {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.calendar-controls select {
    padding: 0.3rem 0.6rem;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    background-color: var(--bg-primary);
    color: var(--text-main);
    font-size: 0.9rem;
    font-weight: 600;
}

.days-wrapper {
    display: flex;
    gap: 0.5rem;
    overflow-x: auto;
    padding-bottom: 0.5rem;
    scrollbar-width: thin;
    scrollbar-color: var(--accent-color) transparent;
}

.days-wrapper::-webkit-scrollbar {
    height: 4px;
}

.days-wrapper::-webkit-scrollbar-thumb {
    background: var(--accent-color);
    border-radius: 10px;
}

.day-item {
    flex: 0 0 40px;
    height: 45px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
    background-color: var(--bg-primary);
}

.day-item:hover {
    border-color: var(--accent-color);
}

.day-item.active {
    background-color: var(--accent-color);
    color: var(--accent-contrast);
    border-color: var(--accent-color);
}

.day-name {
    font-size: 0.6rem;
    text-transform: uppercase;
    font-weight: 700;
}

.day-number {
    font-size: 1rem;
    font-weight: 700;
}

.filter-bar {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.filter-btn {
    background: none;
    border: 1px solid var(--border-color);
    padding: 0.3rem 0.8rem;
    border-radius: 20px;
    font-size: 0.8rem;
    color: var(--text-muted);
    cursor: pointer;
    transition: var(--transition);
}

.filter-btn.active {
    background-color: var(--accent-color);
    color: var(--accent-contrast);
    border-color: var(--accent-color);
}

/* Todo List */
ul {
    list-style: none;
}

.todo-item {
    display: flex;
    align-items: center;
    padding: 1rem;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    margin-bottom: 0.75rem;
    transition: var(--transition);
}

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

.todo-item.completed .todo-text {
    text-decoration: line-through;
}

.todo-checkbox {
    margin-right: 1rem;
    width: 1.2rem;
    height: 1.2rem;
    cursor: pointer;
}

.todo-content {
    flex-grow: 1;
}

.todo-text {
    display: block;
    font-weight: 500;
}

.todo-meta {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.todo-badge {
    display: inline-block;
    padding: 0.1rem 0.4rem;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    margin-right: 0.4rem;
    text-transform: uppercase;
    font-size: 0.65rem;
}

.delete-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    font-size: 1.2rem;
    padding-left: 1rem;
}

.delete-btn:hover {
    color: #ff4444;
}

/* Theme Toggle Logic */
[data-theme='dark'] .sun { display: none; }
[data-theme='light'] .moon { display: none; }
body:not([data-theme]) .moon { display: none; }

@media (max-width: 480px) {
    .options-group {
        grid-template-columns: 1fr;
    }
}