:root {
    --bg-primary: #f5f5f5;
    --bg-secondary: white;
    --bg-tertiary: #f8f9fa;
    --text-primary: #333;
    --text-secondary: #666;
    --border-color: #eee;
    --border-light: #ddd;
    --day-default: #ebedf0;
    --day-completed: #39d353;
    --day-today: #0969da;
    --shadow: rgba(0,0,0,0.1);
}

[data-theme="dark"] {
    --bg-primary: #1a1a1a;
    --bg-secondary: #2d2d2d;
    --bg-tertiary: #333;
    --text-primary: #e0e0e0;
    --text-secondary: #b0b0b0;
    --border-color: #404040;
    --border-light: #555;
    --day-default: #404040;
    --day-completed: #28a745;
    --day-today: #007bff;
    --shadow: rgba(0,0,0,0.3);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    max-width: 900px;
    margin: 0 auto;
    padding: 12px;
    background: var(--bg-primary);
    color: var(--text-primary);
    transition: background-color 0.3s ease, color 0.3s ease;
}

@media (max-width: 768px) {
    body {
        padding: 8px;
    }
}

.container {
    background: var(--bg-secondary);
    border-radius: 8px;
    padding: 20px;
    box-shadow: 0 2px 4px var(--shadow);
    transition: background-color 0.3s ease;
}

@media (max-width: 768px) {
    .container {
        padding: 16px;
        border-radius: 4px;
    }
}

h1 {
    margin: 0 0 20px 0;
    color: var(--text-primary);
    font-size: 28px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.theme-switcher {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 8px 12px;
    border-radius: 6px;
    cursor: pointer;
    font-size: 14px;
    transition: all 0.3s ease;
    min-height: auto;
}

.theme-switcher:hover {
    background: var(--border-color);
}

@media (max-width: 768px) {
    h1 {
        font-size: 24px;
        margin: 0 0 16px 0;
    }
}

.add-habit {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
    flex-wrap: wrap;
}

@media (max-width: 768px) {
    .add-habit {
        flex-direction: column;
        gap: 12px;
    }
}

.sort-controls {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 24px;
    padding: 12px;
    background: var(--bg-tertiary);
    border-radius: 6px;
    transition: background-color 0.3s ease;
}

.sort-controls label {
    font-size: 14px;
    color: var(--text-secondary);
    font-weight: 500;
}

.sort-controls select {
    padding: 8px 12px;
    border: 1px solid var(--border-light);
    border-radius: 6px;
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 14px;
    cursor: pointer;
    transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease;
}

.sort-controls select:focus {
    outline: none;
    border-color: #007AFF;
}

@media (max-width: 768px) {
    .sort-controls {
        flex-direction: column;
        align-items: stretch;
        gap: 8px;
    }
    
    .sort-controls select {
        width: 100%;
    }
}

.import-export {
    display: flex;
    gap: 8px;
    margin-top: 24px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
    flex-wrap: wrap;
    justify-content: center;
}

@media (max-width: 768px) {
    .import-export {
        flex-direction: column;
        gap: 12px;
        margin-top: 20px;
    }
}

.footer-notice {
    margin-top: 20px;
    padding: 16px;
    background: var(--bg-tertiary);
    border-radius: 6px;
    font-size: 13px;
    line-height: 1.5;
    color: var(--text-secondary);
    text-align: center;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.footer-notice a {
    color: #007AFF;
    text-decoration: none;
}

.footer-notice a:hover {
    text-decoration: underline;
}

@media (max-width: 768px) {
    .footer-notice {
        font-size: 12px;
        padding: 12px;
        margin-top: 16px;
    }
}

input[type="text"] {
    flex: 1;
    padding: 12px 16px;
    border: 1px solid var(--border-light);
    border-radius: 8px;
    font-size: 16px;
    min-height: 44px;
    box-sizing: border-box;
    background: var(--bg-secondary);
    color: var(--text-primary);
    transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease;
}

@media (max-width: 768px) {
    input[type="text"] {
        width: 100%;
        font-size: 16px;
    }
}

button {
    padding: 12px 20px;
    background: #007AFF;
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 16px;
    min-height: 44px;
    touch-action: manipulation;
}

@media (max-width: 768px) {
    button {
        width: 100%;
        padding: 14px 20px;
        font-size: 16px;
    }
}

button:hover {
    background: #0056CC;
}

.habit {
    margin-bottom: 24px;
    padding: 16px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    transition: border-color 0.3s ease;
}

@media (max-width: 768px) {
    .habit {
        margin-bottom: 20px;
        padding: 12px;
    }
}

.habit-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 16px;
    gap: 12px;
}

@media (max-width: 768px) {
    .habit-header {
        flex-direction: column;
        align-items: stretch;
        gap: 8px;
    }
}

.habit-name {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
}

.habit-stats {
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 14px;
    color: var(--text-secondary);
    flex-wrap: wrap;
}

@media (max-width: 768px) {
    .habit-stats {
        flex-direction: column;
        align-items: stretch;
        gap: 8px;
        font-size: 13px;
    }
}

.delete-btn, .rename-btn {
    padding: 6px 12px;
    font-size: 13px;
    min-height: auto;
}

.delete-btn {
    background: #FF3B30;
}

.rename-btn {
    background: #007AFF;
}

@media (max-width: 768px) {
    .delete-btn, .rename-btn {
        width: 100%;
        padding: 10px 12px;
        font-size: 14px;
    }
}

.delete-btn:hover {
    background: #D70015;
}

.calendar {
    display: flex;
    flex-direction: column;
    gap: 4px;
    overflow-x: auto;
}

@media (max-width: 768px) {
    .calendar {
        gap: 2px;
    }
}

.calendar-header {
    display: grid;
    grid-template-columns: repeat(53, 12px);
    gap: 2px;
    margin-bottom: 8px;
    font-size: 10px;
    color: var(--text-secondary);
    overflow-x: auto;
}

@media (max-width: 768px) {
    .calendar-header {
        grid-template-columns: repeat(53, 8px);
        gap: 1px;
        font-size: 8px;
    }
}

.month-label {
    grid-column: span 4;
    text-align: left;
}

.calendar-grid {
    display: grid;
    grid-template-columns: repeat(53, 12px);
    gap: 2px;
    overflow-x: auto;
}

@media (max-width: 768px) {
    .calendar-grid {
        grid-template-columns: repeat(53, 8px);
        gap: 1px;
    }
}

.day-square {
    width: 12px;
    height: 12px;
    background: var(--day-default);
    border-radius: 2px;
    cursor: pointer;
    position: relative;
    touch-action: manipulation;
    transition: background-color 0.3s ease;
}

@media (max-width: 768px) {
    .day-square {
        width: 8px;
        height: 8px;
        border-radius: 1px;
    }
}

.day-square:hover {
    outline: 1px solid #333;
}

.day-square.completed {
    background: var(--day-completed);
}

.day-square.today {
    outline: 2px solid var(--day-today);
}

.tooltip {
    position: fixed;
    bottom: auto;
    top: auto;
    left: auto;
    right: auto;
    transform: none;
    background: var(--text-primary);
    color: var(--bg-secondary);
    padding: 6px 10px;
    border-radius: 4px;
    font-size: 12px;
    white-space: nowrap;
    opacity: 0;
    pointer-events: none;
    z-index: 1000;
    transition: opacity 0.2s ease;
}

.day-square:hover .tooltip {
    opacity: 1;
}

.year-controls {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 16px;
    margin-bottom: 16px;
    padding: 8px;
    background: var(--bg-tertiary);
    border-radius: 6px;
    transition: background-color 0.3s ease;
}

.year-btn {
    background: #6c757d;
    color: white;
    border: none;
    padding: 6px 12px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 14px;
    min-width: 40px;
}

.year-btn:hover {
    background: #5a6268;
}

.year-btn:disabled {
    background: #dee2e6;
    color: #6c757d;
    cursor: not-allowed;
}

.current-year {
    font-size: 16px;
    font-weight: 600;
    color: var(--text-primary);
    min-width: 60px;
    text-align: center;
}