/* --- 디자인 시스템 변수 정의 (CSS Variables) --- */
:root {
    /* 라이트 모드 컬러셋 */
    --bg-app: #f8fafc;
    --bg-sidebar: #ffffff;
    --bg-editor: #ffffff;
    
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    
    --accent: #4f46e5;
    --accent-hover: #4338ca;
    --accent-light: #e0e7ff;
    
    --border-color: #f1f5f9;
    --border-hover: #e2e8f0;
    
    --active-item-bg: #f1f5f9;
    --hover-item-bg: #f8fafc;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.05), 0 4px 6px -4px rgba(0, 0, 0, 0.05);
    
    --transition-speed: 0.25s;
    --font-heading: 'Outfit', sans-serif;
    --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

/* 다크 모드 속성 정의 */
[data-theme="dark"] {
    --bg-app: #0f0f11;
    --bg-sidebar: #151518;
    --bg-editor: #1b1b1f;
    
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    
    --accent: #6366f1;
    --accent-hover: #4f46e5;
    --accent-light: #1e1b4b;
    
    --border-color: #27272a;
    --border-hover: #3f3f46;
    
    --active-item-bg: #27272a;
    --hover-item-bg: #1e1e22;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.25), 0 2px 4px -2px rgba(0, 0, 0, 0.25);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
}

/* --- 초기화 및 기본 스타일 --- */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: var(--font-body);
    background-color: var(--bg-app);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    transition: background-color var(--transition-speed), color var(--transition-speed);
    height: 100vh;
    overflow: hidden;
}

/* --- 레이아웃 컨테이너 --- */
.app-container {
    display: flex;
    width: 100vw;
    height: 100vh;
    position: relative;
}

/* --- 모바일 헤더 --- */
.mobile-header {
    display: none; /* 기본적으로 숨김 (PC 환경) */
    width: 100%;
    height: 60px;
    background-color: var(--bg-sidebar);
    border-bottom: 1px solid var(--border-color);
    padding: 0 16px;
    align-items: center;
    justify-content: space-between;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 100;
}

.mobile-header .logo {
    font-family: var(--font-heading);
    font-size: 1.25rem;
    font-weight: 600;
}

.mobile-header button {
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    padding: 8px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color var(--transition-speed);
}

.mobile-header button:hover {
    background-color: var(--hover-item-bg);
}

/* --- 사이드바 --- */
.sidebar {
    width: 320px;
    height: 100%;
    background-color: var(--bg-sidebar);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    flex-shrink: 0;
    transition: transform var(--transition-speed) cubic-bezier(0.4, 0, 0.2, 1), 
                background-color var(--transition-speed), 
                border-color var(--transition-speed);
    z-index: 150;
}

.sidebar-header {
    padding: 24px;
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.logo {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: -0.025em;
    color: var(--text-primary);
}

/* --- 공통 버튼 스타일 --- */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    font-family: var(--font-body);
    font-size: 0.9rem;
    font-weight: 500;
    padding: 12px 16px;
    border-radius: 10px;
    border: none;
    cursor: pointer;
    transition: all var(--transition-speed);
    width: 100%;
}

.btn-primary {
    background-color: var(--accent);
    color: #ffffff;
}

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

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

.btn-icon {
    background: none;
    border: none;
    color: var(--text-secondary);
    padding: 8px;
    border-radius: 8px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-speed);
}

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

/* --- 검색 박스 --- */
.search-box {
    margin: 0 24px 16px 24px;
    position: relative;
    display: flex;
    align-items: center;
}

.search-icon {
    position: absolute;
    left: 14px;
    color: var(--text-muted);
    pointer-events: none;
}

.search-box input {
    width: 100%;
    padding: 12px 12px 12px 40px;
    border-radius: 10px;
    border: 1px solid var(--border-color);
    background-color: var(--bg-app);
    color: var(--text-primary);
    font-family: var(--font-body);
    font-size: 0.9rem;
    outline: none;
    transition: all var(--transition-speed);
}

.search-box input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-light);
    background-color: var(--bg-sidebar);
}

/* --- 카테고리 탭 --- */
.category-tabs {
    display: flex;
    gap: 8px;
    padding: 0 24px;
    margin-bottom: 12px;
    overflow-x: auto;
    scrollbar-width: none; /* Firefox */
}

.category-tabs::-webkit-scrollbar {
    display: none; /* Chrome, Safari */
}

.category-tab {
    padding: 6px 12px;
    font-size: 0.8rem;
    font-weight: 500;
    border-radius: 20px;
    border: 1px solid var(--border-color);
    background-color: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    white-space: nowrap;
    transition: all var(--transition-speed);
}

.category-tab:hover {
    background-color: var(--hover-item-bg);
    border-color: var(--border-hover);
}

.category-tab.active {
    background-color: var(--accent-light);
    color: var(--accent);
    border-color: transparent;
}

/* --- 메모 목록 영역 --- */
.note-list-container {
    flex-grow: 1;
    overflow-y: auto;
    padding: 0 16px;
    scrollbar-width: thin;
    scrollbar-color: var(--border-color) transparent;
}

.note-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.note-item {
    padding: 16px;
    border-radius: 10px;
    cursor: pointer;
    background-color: transparent;
    border: 1px solid transparent;
    transition: all var(--transition-speed);
    display: flex;
    flex-direction: column;
    gap: 6px;
    position: relative;
    overflow: hidden;
}

.note-item:hover {
    background-color: var(--hover-item-bg);
    border-color: var(--border-color);
}

.note-item.active {
    background-color: var(--active-item-bg);
    border-color: var(--border-hover);
}

.note-item.active::before {
    content: '';
    position: absolute;
    left: 0;
    top: 15%;
    height: 70%;
    width: 4px;
    background-color: var(--accent);
    border-radius: 0 4px 4px 0;
}

.note-item-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.note-item-title {
    font-weight: 600;
    font-size: 0.95rem;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    width: 100%;
}

.note-item-excerpt {
    font-size: 0.85rem;
    color: var(--text-secondary);
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
    text-overflow: ellipsis;
    line-height: 1.4;
}

.note-item-meta {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-top: 4px;
}

.note-item-date {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.note-item-category {
    font-size: 0.75rem;
    font-weight: 500;
    padding: 2px 8px;
    border-radius: 12px;
    background-color: var(--border-color);
    color: var(--text-secondary);
    text-transform: capitalize;
}

/* --- 사이드바 푸터 (테마 전환) --- */
.sidebar-footer {
    padding: 16px 24px;
    border-top: 1px solid var(--border-color);
}

.theme-toggle-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    width: 100%;
    padding: 12px;
    border-radius: 10px;
    background-color: var(--bg-app);
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-family: var(--font-body);
    font-size: 0.85rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-speed);
}

.theme-toggle-btn:hover {
    background-color: var(--hover-item-bg);
    color: var(--text-primary);
    border-color: var(--border-hover);
}

/* 테마 아이콘 토글 로직 */
.sun-icon { display: block; }
.moon-icon { display: none; }

[data-theme="dark"] .sun-icon { display: none; }
[data-theme="dark"] .moon-icon { display: block; }

/* --- 메인 에디터 영역 --- */
.editor-area {
    flex-grow: 1;
    height: 100%;
    background-color: var(--bg-editor);
    display: flex;
    flex-direction: column;
    position: relative;
    transition: background-color var(--transition-speed);
}

.editor-header {
    height: 72px;
    padding: 0 32px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-shrink: 0;
}

.editor-meta {
    display: flex;
    align-items: center;
    gap: 16px;
}

.note-category-select {
    font-family: var(--font-body);
    font-size: 0.85rem;
    font-weight: 500;
    padding: 6px 12px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    background-color: var(--bg-app);
    color: var(--text-secondary);
    outline: none;
    cursor: pointer;
    transition: all var(--transition-speed);
}

.note-category-select:focus {
    border-color: var(--accent);
}

.status-indicator {
    font-size: 0.8rem;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 6px;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.status-indicator.saving {
    opacity: 0.8;
}

.status-indicator.saved {
    opacity: 0.6;
}

.status-indicator::before {
    content: '';
    display: inline-block;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background-color: var(--text-muted);
}

.status-indicator.saving::before {
    background-color: var(--accent);
    animation: pulse 1s infinite alternate;
}

.status-indicator.saved::before {
    background-color: #10b981; /* 녹색 */
}

@keyframes pulse {
    from { opacity: 0.3; transform: scale(0.8); }
    to { opacity: 1; transform: scale(1.2); }
}

.editor-body {
    flex-grow: 1;
    padding: 40px 48px;
    display: flex;
    flex-direction: column;
    gap: 20px;
    overflow-y: auto;
}

#note-title {
    font-family: var(--font-heading);
    font-size: 2rem;
    font-weight: 700;
    border: none;
    outline: none;
    background: transparent;
    color: var(--text-primary);
    width: 100%;
    padding: 8px 0;
    letter-spacing: -0.02em;
}

#note-title::placeholder {
    color: var(--text-muted);
    font-weight: 600;
}

#note-content {
    font-family: var(--font-body);
    font-size: 1.05rem;
    border: none;
    outline: none;
    background: transparent;
    color: var(--text-primary);
    width: 100%;
    flex-grow: 1;
    resize: none;
    line-height: 1.7;
}

#note-content::placeholder {
    color: var(--text-muted);
}

/* --- 에디터 엠프티 상태 --- */
.empty-state {
    position: absolute;
    inset: 0;
    background-color: var(--bg-editor);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 20px;
    color: var(--text-muted);
    z-index: 10;
    transition: opacity var(--transition-speed);
}

.empty-state svg {
    color: var(--text-muted);
    opacity: 0.6;
}

.empty-state p {
    font-size: 0.95rem;
    font-weight: 500;
}

.empty-state .btn {
    width: auto;
    padding: 10px 24px;
}

/* 모바일 오버레이 */
.sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background-color: rgba(0, 0, 0, 0.4);
    z-index: 120;
    opacity: 0;
    transition: opacity var(--transition-speed);
}

/* --- 반응형 레이아웃 미디어 쿼리 --- */
@media (max-width: 768px) {
    .mobile-header {
        display: flex;
    }
    
    .sidebar {
        position: fixed;
        left: 0;
        top: 0;
        bottom: 0;
        transform: translateX(-100%);
        box-shadow: var(--shadow-lg);
    }
    
    .sidebar.open {
        transform: translateX(0);
    }
    
    .sidebar-overlay.open {
        display: block;
        opacity: 1;
    }
    
    .editor-area {
        margin-top: 60px;
        height: calc(100% - 60px);
    }
    
    .editor-header {
        padding: 0 20px;
        height: 60px;
    }
    
    .editor-body {
        padding: 24px 20px;
        gap: 16px;
    }
    
    #note-title {
        font-size: 1.5rem;
    }
    
    #note-content {
        font-size: 0.95rem;
    }
}