/* CSS Variables */
:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --primary-light: #e0e7ff;
    --success-color: #10b981;
    --success-light: #d1fae5;
    --danger-color: #ef4444;
    --danger-hover: #dc2626;
    --warning-color: #f59e0b;
    --background-color: #f8fafc;
    --surface-color: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --transition: all 0.2s ease;
}

/* Reset and Base Styles */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background-color: var(--background-color);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* App Container */
.app-container {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* Header */
.header {
    background: linear-gradient(135deg, var(--primary-color) 0%, #8b5cf6 100%);
    color: white;
    padding: 2rem 1rem;
    text-align: center;
}

.header-content {
    max-width: 800px;
    margin: 0 auto;
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    margin-bottom: 0.5rem;
}

.logo-img {
    width: 48px;
    height: 48px;
    border-radius: var(--radius-md);
}

.logo h1 {
    font-size: 2rem;
    font-weight: 700;
    letter-spacing: -0.5px;
}

.tagline {
    font-size: 1.1rem;
    opacity: 0.9;
}

/* Main Content */
.main-content {
    flex: 1;
    max-width: 900px;
    margin: 0 auto;
    padding: 1.5rem 1rem;
    width: 100%;
}

/* Section Styles */
section {
    background: var(--surface-color);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow-md);
}

section h2 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

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

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

/* Add Habit Form */
.add-habit-form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

input[type="text"],
select {
    width: 100%;
    padding: 0.75rem 1rem;
    font-size: 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--surface-color);
    color: var(--text-primary);
    transition: var(--transition);
}

input[type="text"]:focus,
select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--primary-light);
}

input[type="text"]::placeholder {
    color: var(--text-muted);
}

input[type="color"] {
    width: 100%;
    height: 44px;
    padding: 4px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    cursor: pointer;
    background: var(--surface-color);
}

input[type="color"]::-webkit-color-swatch-wrapper {
    padding: 2px;
}

input[type="color"]::-webkit-color-swatch {
    border-radius: var(--radius-sm);
    border: none;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: var(--transition);
}

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

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
}

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

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

.btn-icon-only {
    width: 36px;
    height: 36px;
    padding: 0;
    background: var(--background-color);
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 1rem;
}

.btn-icon-only:hover {
    background: var(--border-color);
    color: var(--text-primary);
}

.btn-icon {
    font-size: 1.25rem;
    font-weight: 400;
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
}

.stat-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 1rem;
    background: var(--background-color);
    border-radius: var(--radius-md);
    text-align: center;
}

.stat-icon {
    font-size: 1.5rem;
    margin-bottom: 0.25rem;
}

.stat-value {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--primary-color);
}

.stat-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Date Display */
.date-display {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.date-display span {
    font-weight: 600;
    color: var(--text-secondary);
    min-width: 140px;
    text-align: center;
}

/* Habits List */
.habits-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.habit-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem;
    background: var(--background-color);
    border-radius: var(--radius-md);
    border-left: 4px solid var(--primary-color);
    transition: var(--transition);
}

.habit-item:hover {
    box-shadow: var(--shadow-sm);
}

.habit-item.completed {
    background: var(--success-light);
    border-left-color: var(--success-color);
}

.habit-checkbox {
    width: 28px;
    height: 28px;
    border: 2px solid var(--border-color);
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
    flex-shrink: 0;
    background: var(--surface-color);
}

.habit-checkbox:hover {
    border-color: var(--primary-color);
    background: var(--primary-light);
}

.habit-item.completed .habit-checkbox {
    background: var(--success-color);
    border-color: var(--success-color);
    color: white;
}

.habit-checkbox::after {
    content: '';
}

.habit-item.completed .habit-checkbox::after {
    content: '✓';
    font-size: 14px;
    font-weight: bold;
}

.habit-icon {
    font-size: 1.5rem;
    flex-shrink: 0;
}

.habit-info {
    flex: 1;
    min-width: 0;
}

.habit-name {
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
    word-break: break-word;
}

.habit-item.completed .habit-name {
    text-decoration: line-through;
    color: var(--text-secondary);
}

.habit-streak {
    display: flex;
    align-items: center;
    gap: 0.25rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.habit-streak.active {
    color: var(--warning-color);
}

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

.habit-edit-btn {
    width: 32px;
    height: 32px;
    border: none;
    background: transparent;
    color: var(--text-muted);
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: var(--transition);
    font-size: 1rem;
}

.habit-edit-btn:hover {
    background: var(--border-color);
    color: var(--text-primary);
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: 3rem 1rem;
    color: var(--text-secondary);
}

.empty-icon {
    font-size: 3rem;
    display: block;
    margin-bottom: 1rem;
    opacity: 0.5;
}

.empty-state p {
    font-size: 1rem;
}

/* Calendar */
.calendar-container {
    margin-bottom: 1rem;
}

.calendar-nav {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.calendar-nav span {
    font-weight: 600;
    color: var(--text-secondary);
    min-width: 140px;
    text-align: center;
}

.calendar-header {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 4px;
    margin-bottom: 8px;
}

.calendar-header span {
    text-align: center;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-muted);
    padding: 0.5rem 0;
}

.calendar-grid {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 4px;
}

.calendar-day {
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.875rem;
    border-radius: var(--radius-sm);
    background: var(--background-color);
    color: var(--text-secondary);
    cursor: pointer;
    transition: var(--transition);
    position: relative;
}

.calendar-day:hover {
    background: var(--border-color);
}

.calendar-day.empty {
    background: transparent;
    cursor: default;
}

.calendar-day.today {
    font-weight: 700;
    box-shadow: inset 0 0 0 2px var(--primary-color);
}

.calendar-day.partial {
    background: var(--warning-color);
    color: white;
}

.calendar-day.complete {
    background: var(--success-color);
    color: white;
}

.calendar-day.future {
    opacity: 0.4;
    cursor: not-allowed;
}

/* Calendar Legend */
.calendar-legend {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    justify-content: center;
    padding-top: 0.5rem;
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.legend-color {
    width: 16px;
    height: 16px;
    border-radius: var(--radius-sm);
}

.legend-none {
    background: var(--background-color);
    border: 1px solid var(--border-color);
}

.legend-partial {
    background: var(--warning-color);
}

.legend-full {
    background: var(--success-color);
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    align-items: center;
    justify-content: center;
    padding: 1rem;
}

.modal.active {
    display: flex;
}

.modal-content {
    background: var(--surface-color);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    width: 100%;
    max-width: 400px;
    box-shadow: var(--shadow-lg);
}

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

.modal-header h3 {
    font-size: 1.25rem;
    font-weight: 600;
}

.modal-close {
    width: 32px;
    height: 32px;
    border: none;
    background: transparent;
    font-size: 1.5rem;
    color: var(--text-muted);
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

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

.modal-actions {
    display: flex;
    gap: 1rem;
    margin-top: 1.5rem;
}

.modal-actions .btn {
    flex: 1;
}

/* Footer */
.footer {
    background: var(--surface-color);
    border-top: 1px solid var(--border-color);
    padding: 1.5rem 1rem;
    text-align: center;
}

.footer p {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
}

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

/* Responsive Design */
@media (min-width: 640px) {
    .stats-grid {
        grid-template-columns: repeat(4, 1fr);
    }

    .add-habit-form {
        flex-direction: row;
        flex-wrap: wrap;
        align-items: flex-end;
    }

    .add-habit-form .form-group:first-child {
        flex: 1;
        min-width: 200px;
    }

    .add-habit-form .form-row {
        width: auto;
    }

    .add-habit-form .btn {
        height: 44px;
    }
}

@media (max-width: 480px) {
    .header {
        padding: 1.5rem 1rem;
    }

    .logo h1 {
        font-size: 1.5rem;
    }

    .tagline {
        font-size: 0.9rem;
    }

    section {
        padding: 1rem;
    }

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

    .calendar-day {
        font-size: 0.75rem;
    }

    .habit-item {
        padding: 0.75rem;
    }

    .habit-icon {
        font-size: 1.25rem;
    }

    .form-row {
        grid-template-columns: 1fr 80px;
    }
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.habit-item {
    animation: fadeIn 0.3s ease;
}

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

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

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

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