:root {
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --bg-page: #f8fafc;
    --bg-surface: #ffffff;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --border-hover: #cbd5e1;
    --danger: #ef4444;
    --success: #10b981;
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.05), 0 2px 4px -2px rgb(0 0 0 / 0.05);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.05), 0 4px 6px -4px rgb(0 0 0 / 0.05);
    --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
    --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: var(--font-sans);
    background-color: var(--bg-page);
    color: var(--text-main);
    line-height: 1.5;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    padding: 2rem 1rem;
    -webkit-font-smoothing: antialiased;
}

.app-container {
    width: 100%;
    max-width: 600px;
}

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

.date-header-wrapper {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.nav-btn {
    border-radius: 50%;
    width: 40px;
    height: 40px;
    background-color: var(--bg-surface);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    flex-shrink: 0;
}

.nav-btn:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--border-hover);
    transform: translateY(-2px);
    color: var(--text-main);
}

.native-date-picker {
    border: 1px solid var(--border);
    background-color: transparent;
    color: var(--text-muted);
    font-family: var(--font-sans);
    padding: 0.5rem;
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    cursor: pointer;
    outline: none;
    transition: var(--transition);
    margin-left: 0.5rem;
}

.native-date-picker:hover {
    border-color: var(--primary);
    background-color: var(--bg-surface);
}

.date-header h1 {
    font-size: 2rem;
    font-weight: 600;
    letter-spacing: -0.025em;
    color: var(--text-main);
    margin-bottom: 0.25rem;
}

.date-header span {
    font-size: 0.95rem;
    color: var(--text-muted);
    font-weight: 400;
}

/* Buttons */
.icon-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 0.5rem;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

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

.primary-btn {
    background-color: var(--primary);
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 500;
    font-size: 0.95rem;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

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

.primary-btn.full-width {
    width: 100%;
    margin-top: 1rem;
}

/* Sync Status */
.sync-status {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 1rem;
    font-size: 0.85rem;
    color: var(--text-muted);
}

.status-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background-color: var(--success);
}

.sync-status.syncing .status-dot {
    background-color: #f59e0b;
    /* yellow */
    animation: pulse 1.5s infinite;
}

.sync-status.error .status-dot {
    background-color: var(--danger);
}

@keyframes pulse {
    0% {
        opacity: 1;
    }

    50% {
        opacity: 0.5;
    }

    100% {
        opacity: 1;
    }
}

/* Main Input */
.todo-input-group {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 2rem;
}

#todo-input {
    flex: 1;
    padding: 1rem 1.25rem;
    font-size: 1rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    background-color: var(--bg-surface);
    color: var(--text-main);
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
    outline: none;
    font-family: inherit;
}

#todo-input:focus, .recurrence-select:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

#todo-input::placeholder {
    color: #94a3b8;
}

.recurrence-select {
    padding: 0 1rem;
    font-size: 0.95rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    background-color: var(--bg-surface);
    color: var(--text-main);
    box-shadow: var(--shadow-sm);
    outline: none;
    font-family: inherit;
    cursor: pointer;
    transition: var(--transition);
}

/* Todo List */
.todo-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.todo-item {
    display: flex;
    align-items: center;
    padding: 1rem 1.25rem;
    background-color: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    gap: 1rem;
    animation: slideIn 0.3s ease-out forwards;
}

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

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.todo-item:hover {
    border-color: var(--border-hover);
    box-shadow: var(--shadow-md);
}

.todo-item.dragging {
    opacity: 0.5;
    background-color: var(--bg-page);
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.05);
    transform: scale(0.98);
}

.drag-handle {
    cursor: grab;
    color: #94a3b8;
    opacity: 1;
    display: flex;
    align-items: center;
    padding-right: 0.25rem;
}

.drag-handle:hover {
    color: var(--primary);
}

.drag-handle svg {
    width: 20px;
    height: 20px;
}

.drag-handle:active {
    cursor: grabbing;
}

/* Custom Checkbox */
.checkbox-wrapper {
    display: flex;
    align-items: center;
    position: relative;
    cursor: pointer;
}

.checkbox-wrapper input {
    opacity: 0;
    position: absolute;
    width: 100%;
    height: 100%;
    cursor: pointer;
    z-index: 2;
}

.checkmark {
    width: 22px;
    height: 22px;
    border: 2px solid var(--border-hover);
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
    background-color: white;
}

.checkbox-wrapper input:checked~.checkmark {
    background-color: var(--primary);
    border-color: var(--primary);
}

.checkmark svg {
    color: white;
    width: 14px;
    height: 14px;
    opacity: 0;
    transform: scale(0.5);
    transition: var(--transition);
}

.checkbox-wrapper input:checked~.checkmark svg {
    opacity: 1;
    transform: scale(1);
}

.todo-text {
    flex: 1;
    font-size: 1rem;
    color: var(--text-main);
    word-break: break-word;
    transition: color 0.3s, background-color 0.2s;
    padding: 0.25rem 0.5rem;
    border-radius: var(--radius-sm);
    border: 1px solid transparent;
    outline: none;
}

.todo-text[contenteditable="true"] {
    background-color: var(--bg-page);
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(37, 99, 235, 0.1);
    cursor: text;
}

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

.delete-btn {
    background: none;
    border: none;
    color: #cbd5e1;
    cursor: pointer;
    padding: 0.25rem;
    border-radius: var(--radius-sm);
    transition: var(--transition);
    opacity: 0;
}

.todo-item:hover .delete-btn {
    opacity: 1;
}

.delete-btn:hover {
    color: var(--danger);
    background-color: #fee2e2;
}

/* Completed Section */
.completed-section {
    margin-top: 2.5rem;
}

.section-title {
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    margin-bottom: 1rem;
    font-weight: 600;
}

.completed-section .todo-item {
    background-color: #f1f5f9;
    border-color: transparent;
    box-shadow: none;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(15, 23, 42, 0.4);
    backdrop-filter: blur(4px);
    z-index: 100;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity 0.3s;
}

.modal.active {
    display: flex;
    opacity: 1;
}

.modal-content {
    background-color: var(--bg-surface);
    border-radius: var(--radius-lg);
    width: 100%;
    max-width: 450px;
    padding: 2rem;
    box-shadow: var(--shadow-lg);
    transform: scale(0.95);
    transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.modal.active .modal-content {
    transform: scale(1);
}

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

.modal-header h2 {
    font-size: 1.5rem;
    font-weight: 600;
}

.close-btn {
    font-size: 1.5rem;
    color: var(--text-muted);
}

.settings-helper {
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-bottom: 1.5rem;
}

.form-group {
    margin-bottom: 1.25rem;
}

.form-group label {
    display: flex;
    justify-content: space-between;
    font-size: 0.9rem;
    font-weight: 500;
    margin-bottom: 0.5rem;
    color: var(--text-main);
}

.help-link {
    font-size: 0.8rem;
    color: var(--primary);
    text-decoration: none;
}

.help-link:hover {
    text-decoration: underline;
}

.form-group input {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    transition: var(--transition);
    outline: none;
    background-color: var(--bg-page);
    font-family: var(--font-sans);
}

.form-group input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}