:root {
    --stm-bg: #ffffff;
    --stm-primary: #0d6efd;
    --stm-text: #334155;
    --stm-shadow: 0 12px 40px rgba(0,0,0,0.08);
}

body { /*background-color: #f8fafc;*/ padding-top: 65px; }

/* --- 基礎結構 --- */
.nav-stm-navbar { 
    background-color: var(--stm-bg) !important; 
    z-index: 1050; 
    border-bottom: 1px solid #eef2f6;
}
.nav-stm-brand { padding:10px 0; font-weight: 700; color: var(--stm-text) !important; text-decoration: none; font-size: 1.25rem; }
.nav-stm-link { 
    color: var(--stm-text) !important; font-weight: 900; padding: 0.5rem 1.2rem !important; 
    text-decoration: none; display: flex; align-items: center; justify-content: space-between; 
}

/* --- 箭頭旋轉邏輯 (核心修正) --- */
.nav-stm-arrow {
    display: inline-block;
    font-size: 0.75rem;
    transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    margin-left: 8px;
    opacity: 0.5;
}

/* 桌面端狀態 */
@media (min-width: 992px) {
    .nav-stm-dropdown.nav-stm-is-active > .nav-stm-link .nav-stm-arrow { transform: rotate(90deg); }
    .nav-stm-dropdown-submenu.nav-stm-is-active > .nav-stm-dropdown-item .nav-stm-arrow { transform: rotate(0deg); }
    /* 邊界偵測向左開時，箭頭指左 */
    .nav-stm-dropdown-submenu.nav-stm-drop-start > .nav-stm-dropdown-item .nav-stm-arrow { transform: rotate(180deg); }
}

/* 手機端狀態 */
@media (max-width: 991px) {
    .nav-stm-is-active > .nav-stm-link .nav-stm-arrow,
    .nav-stm-is-active > .nav-stm-dropdown-item .nav-stm-arrow {
        transform: rotate(180deg) !important;
    }
}

/* --- 桌面端選單顯示 --- */
@media (min-width: 992px) {
    .nav-stm-dropdown-menu {
        display: block !important; visibility: hidden; opacity: 0;
        transform: translateY(10px); transition: all 0.2s ease;
        pointer-events: none; position: absolute; background: #fff;
        list-style: none; padding: 0.6rem; border: 1px solid #f1f5f9;
        border-radius: 12px; box-shadow: var(--stm-shadow); min-width: 210px;
    }

    .nav-stm-dropdown.nav-stm-is-active > .nav-stm-dropdown-menu,
    .nav-stm-dropdown-submenu.nav-stm-is-active > .nav-stm-dropdown-menu {
        visibility: visible; opacity: 1; transform: translateY(0); pointer-events: auto;
    }

    .nav-stm-dropdown { position: relative; }
    .nav-stm-dropdown-submenu { position: relative; }
    .nav-stm-dropdown-submenu > .nav-stm-dropdown-menu { top: 0; left: 100%; margin-left: 2px; margin-top: -5px; }
    .nav-stm-dropdown-submenu.nav-stm-drop-start > .nav-stm-dropdown-menu { left: auto; right: 100%; margin-right: 2px; }

    .nav-stm-dropdown-submenu > .nav-stm-dropdown-menu::before {
        content: ""; position: absolute; top: 0; left: -20px; width: 25px; height: 100%;
    }
}

/* --- 手機端佈局 --- */
@media (max-width: 991px) {
    .nav-stm-dropdown-menu { 
        display: none; visibility: visible !important; opacity: 1 !important;
        position: static !important; width: 100% !important; background: #f8fafc;
        border-left: 2px solid #e2e8f0; margin-left: 1rem !important; list-style: none; padding: 0.5rem;
    }
    .nav-stm-collapse { background: #ffffff; padding: 1rem; border-radius: 12px; margin-top: 8px; box-shadow: 0 5px 15px rgba(0,0,0,0.05); }
}

.nav-stm-dropdown-item { 
    border-radius: 8px; padding: 0.6rem 1rem; color: var(--stm-text); 
    display: flex; justify-content: space-between; align-items: center;
    text-decoration: none; transition: all 0.2s;
}
.nav-stm-dropdown-item:hover { background-color: #f0f7ff; color: var(--stm-primary); transform: translateX(4px); }