.sidebar { 
    width: var(--sidebar-width); 
    height: 100vh;
    background: var(--sidebar); 
    backdrop-filter: blur(10px); 
    border-right: 1px solid rgba(255,255,255,0.05); 
    padding: 2rem 1.2rem; 
    display: flex; 
    flex-direction: column;
    transition: width 0.3s cubic-bezier(0.4, 0, 0.2, 1), padding 0.3s ease;
    flex-shrink: 0;
    overflow: hidden; /* 전체 스크롤을 막고 내부 스크롤 활성화 */
}

.sidebar-content {
    flex: 1;
    overflow-y: auto;
    overflow-x: hidden;
    margin: 0 -0.5rem; /* 스크롤바 공간 확보를 위해 패딩 살짝 조정 */
    padding: 0 0.5rem;
}

/* Custom Scrollbar for Sidebar */
.sidebar-content::-webkit-scrollbar {
    width: 4px;
}

.sidebar-content::-webkit-scrollbar-track {
    background: transparent;
}

.sidebar-content::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.1);
    border-radius: 10px;
}

.sidebar-content::-webkit-scrollbar-thumb:hover {
    background: rgba(56, 189, 248, 0.3);
}

.sidebar-header { margin-bottom: 2.5rem; white-space: nowrap; overflow: hidden; }

.logo { 
    font-size: 1.3rem; 
    font-weight: 800; 
    background: linear-gradient(135deg, #38bdf8, #8b5cf6); 
    -webkit-background-clip: text; 
    -webkit-text-fill-color: transparent; 
    transition: opacity 0.2s; 
}

.sidebar-toggle {
    background: none; border: none; color: var(--muted); font-size: 1.2rem; cursor: pointer;
    padding: 5px; border-radius: 4px; transition: background 0.2s, color 0.2s;
}

.sidebar-toggle:hover { background: rgba(255,255,255,0.05); color: var(--text); }

/* Navigation List */
.nav { list-style: none; display: flex; flex-direction: column; gap: 0; }

.nav li { 
    padding: 0.25rem 0.8rem; 
    border-radius: 4px; 
    font-weight: 600; 
    cursor: pointer; 
    transition: all 0.1s ease; 
    display: flex; 
    align-items: center; 
    gap: 0.6rem; 
    color: var(--muted); 
    font-size: 0.85rem; 
    margin: 0;
    border-top: 1px solid transparent;
}

.nav li:hover { background: rgba(255,255,255,0.05); color: var(--text); }
.nav li.active { background: rgba(56, 189, 248, 0.15); color: var(--accent); }

/* Navigation Dividers */
.nav li:not(.sub-item):not(:first-child) {
    border-top: 1px solid rgba(255, 255, 255, 0.05);
    margin-top: 0.2rem;
    padding-top: 0.4rem;
}

.section-title { 
    font-size: 0.7rem; 
    font-weight: 800; 
    color: rgba(255,255,255,0.25); 
    margin: 0.8rem 0 0.2rem 0.8rem; 
    text-transform: uppercase; 
    letter-spacing: 0.05rem; 
    list-style: none; 
    border-top: 1px solid rgba(255, 255, 255, 0.05); 
    padding-top: 0.5rem; 
}

.sub-item { padding-left: 2.2rem !important; border-top: none !important; margin-top: 0 !important; }

/* Sidebar Footer */
.sidebar-footer {
    display: flex;
    gap: 8px;
    margin-top: auto;
    padding-top: 20px;
    border-top: 1px solid rgba(255,255,255,0.05);
}

.sidebar-footer .action-btn { flex: 1; padding: 10px !important; }

#settingsBtn { 
    flex: 0 0 45px !important; 
    display: flex; 
    justify-content: center; 
    align-items: center; 
    padding: 0 !important; 
    font-size: 1.1rem; 
}

/* Collapsed State (Desktop) */
.sidebar.collapsed { width: var(--sidebar-collapsed-width); padding: 2rem 0.5rem; }
.sidebar.collapsed .text { display: none !important; }
.sidebar.collapsed .logo { width: auto; margin-right: 0; }
.sidebar.collapsed .nav li { padding: 0.8rem 0; justify-content: center; background: none !important; border: none !important; }
.sidebar.collapsed .nav li.active { color: var(--accent); }
.sidebar.collapsed .nav li .icon { font-size: 1.2rem; margin: 0; }
.sidebar.collapsed .section-title { padding: 0.5rem 0; text-align: center; border-top: 1px solid rgba(255,255,255,0.05); height: 1px; overflow: hidden; }
.sidebar.collapsed .sub-item { padding-left: 0 !important; }

/* Hide redundant sections in collapsed state */
.sidebar.collapsed .sidebar-section:has(#calendarHeader),
.sidebar.collapsed .sidebar-section:has(#heatmapContainer),
.sidebar.collapsed #calendarHeader,
.sidebar.collapsed #calendarContainer,
.sidebar.collapsed #heatmapContainer {
    display: none !important;
}

/* Remove boxes from buttons in collapsed state */
.sidebar.collapsed .action-btn {
    background: none !important;
    border: none !important;
    box-shadow: none !important;
    justify-content: center !important;
    padding: 10px 0 !important;
}

.sidebar.collapsed .sidebar-footer { padding: 10px 0; justify-content: center; display: flex; flex-direction: column; align-items: center; border-top: 1px solid rgba(255,255,255,0.05);}
.sidebar.collapsed #logoutBtn { padding: 8px !important; justify-content: center; }
.sidebar.collapsed #settingsBtn { background: none !important; border: none !important; }

/* Tooltips for Collapsed Sidebar */
.sidebar.collapsed [data-tooltip] { position: relative; }
.sidebar.collapsed [data-tooltip]::after {
    content: attr(data-tooltip);
    position: absolute;
    left: 80px;
    top: 50%;
    transform: translateY(-50%);
    background: rgba(15, 23, 42, 0.9);
    color: white;
    padding: 6px 12px;
    border-radius: 6px;
    font-size: 0.8rem;
    white-space: nowrap;
    opacity: 0;
    pointer-events: none;
    transition: all 0.2s ease;
    z-index: 1000;
    border: 1px solid rgba(255, 255, 255, 0.1);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}
.sidebar.collapsed [data-tooltip]:hover::after {
    opacity: 1;
    left: 70px;
}