/* --- Global Reset and Box Sizing --- */
*,
*::before,
*::after {
  box-sizing: border-box; /* Apply border-box universally */
  margin: 0; /* Remove default margins */
  padding: 0; /* Remove default padding */
}

html,
body {
  overflow-x: hidden; /* Prevent horizontal scrolling on the main page */
  width: 100%;      /* Ensure they take full width */
  /* height: 100%; /* Usually handled by min-height on body */
}

/* Remove default list styles */
ul, ol {
    list-style: none;
}

/* Remove default button styles */
button {
    background: none;
    border: none;
    padding: 0;
    font: inherit;
    color: inherit;
    cursor: pointer;
}
/* Ensure links inherit color correctly unless specified */
a {
    color: inherit;
    text-decoration: none; /* Remove default underline */
}


/* --- 字體定義 --- */
@font-face {
  font-family: 'BabelStone Han';
  src: url('../Fonts/BabelStoneHan.woff2') format('woff2');
  font-weight: normal;
  font-style: normal;
}

/* Ghibli 風格調色板和基礎設置 */
:root {
    /* Light Mode */
    --bg-color: #f4f1e9;
    --content-bg: rgba(255, 255, 255, 0.88);
    --nav-bg: rgba(230, 235, 224, 0.85);
    --text-color: #4d453e;
    --text-secondary: #7a726a;
    --header-color: #5c6e58;
    --accent-color: #8db580;
    --border-color: #d3c0a4;
    --button-hover-bg: #d8e0cc;
    --scrollbar-thumb: #b0a89a;
    --scrollbar-track: rgba(230, 235, 224, 0.5);
    --ai-bg: rgba(250, 250, 245, 0.95); /* Fallback AI BG */
    --ai-user-bubble: #cde2c6;
    --ai-ai-bubble: #e8e8e0;
    --shadow-color: rgba(80, 70, 60, 0.1);
    --header-height: 50px;
    --footer-height: 40px;
    --container-v-margin: 40px; /* 估算值，用於 max-height 計算 */
    --layout-gap: clamp(12px, 1.5vw, 20px);
    --side-nav-width: clamp(210px, 22vw, 320px);
    --reading-measure: 52rem;
    /* --- Ghibli Background Colors for Buttons --- */
    --ghibli-color-1: #a8d8ea; /* Light Blue */
    --ghibli-color-2: #d3e0b7; /* Pale Green */
    --ghibli-color-3: #f9cb9c; /* Light Orange */
    --ghibli-color-4: #f4c7c3; /* Soft Pink */
    --ghibli-color-5: #c4b7ea; /* Lavender */
    --ghibli-color-6: #e6d1a1; /* Sand Yellow */
    --ghibli-color-fallback: transparent; /* Fallback color */
    /* --- No Question Text Color --- */
    --no-question-color: #c0392b; /* Darker Red */
}

body.dark-mode {
    /* Dark Mode */
    --bg-color: #3a3f37;
    --content-bg: rgba(40, 45, 38, 0.9);
    --nav-bg: rgba(55, 60, 52, 0.88);
    --text-color: #d8d2c9;
    --text-secondary: #a0988f;
    --header-color: #a8c0a0;
    --accent-color: #709464;
    --border-color: #5e564a;
    --button-hover-bg: #4a5244;
    --scrollbar-thumb: #787168;
    --scrollbar-track: rgba(55, 60, 52, 0.5);
    --ai-bg: rgba(30, 35, 28, 0.95); /* Fallback AI BG Dark */
    --ai-user-bubble: #52694c;
    --ai-ai-bubble: #454a41;
    --shadow-color: rgba(0, 0, 0, 0.2);
    /* --- Dark Mode Ghibli Colors (adjust as needed) --- */
    --ghibli-color-1: #5a7e8a;
    --ghibli-color-2: #6a7857;
    --ghibli-color-3: #a97b5c;
    --ghibli-color-4: #9e7370;
    --ghibli-color-5: #7c6e9a;
    --ghibli-color-6: #9c8b61;
    /* --- Dark Mode No Question Color --- */
    --no-question-color: #e74c3c;
}

body {
    /* Keep existing body styles, but ensure height is managed by flex */
    min-height: 100vh; /* Use min-height instead of height for flexibility */
    display: flex;
    flex-direction: column;
    /* Rest of your body styles... */
    font-family: 'BabelStone Han', 'Noto Serif SC', 'ZCOOL XiaoWei', serif;
    line-height: 1.7;
    background: var(--bg-color) url('../bg.webp') no-repeat center center fixed;
    background-size: cover;
    color: var(--text-color);
    transition: background-color 0.3s ease, color 0.3s ease;
}

header {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 8px  40px 8px 40px;
    overflow: visible;
    background-color: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(5px);
    position: relative;
    border-bottom: 1px solid var(--border-color);
    flex-shrink: 0;
    height: var(--header-height);
    box-sizing: border-box;
}

#main-title {
    margin: 0;
    color: var(--header-color);
    font-family: 'Noto Sans SC', 'BabelStone Han', sans-serif;
    font-size: 1.6em;
    font-weight: 700;
    text-shadow: 1px 1px 2px var(--shadow-color);
    min-width: 0;
}
/* Style for link inside title if you add it back */
#main-title a {
    color: inherit;
    text-decoration: none;
}

#reading-mode-toggle {
    position: absolute;
    left: clamp(12px, 2.5vw, 30px);
    top: 50%;
    transform: translateY(-50%);
    display: inline-flex;
    align-items: center;
    gap: 8px;
    min-height: 36px;
    padding: 5px 10px;
    border: 1px solid color-mix(in srgb, var(--border-color) 76%, transparent);
    border-radius: 8px;
    color: var(--header-color);
    background: color-mix(in srgb, var(--content-bg) 46%, transparent);
    font-family: 'Noto Sans SC', 'BabelStone Han', sans-serif;
    font-size: 0.88rem;
    line-height: 1;
    backdrop-filter: blur(6px);
    transition: color 180ms ease, background-color 180ms ease, border-color 180ms ease, transform 180ms ease;
}

#reading-mode-toggle:hover {
    color: var(--text-color);
    background: color-mix(in srgb, var(--content-bg) 78%, transparent);
    border-color: var(--accent-color);
}

#reading-mode-toggle:focus-visible {
    outline: 3px solid color-mix(in srgb, var(--accent-color) 65%, transparent);
    outline-offset: 2px;
}

#reading-mode-toggle:active {
    transform: translateY(-50%) scale(0.97);
}

.reading-mode-icon {
    display: inline-grid;
    place-items: center;
    width: 1.15em;
    font-size: 1.15em;
}

html.is-reading-focus .reading-mode-icon {
    transform: rotate(180deg);
}


#dark-mode-toggle {
    position: absolute;
    right: 30px;
    top: 50%;
    transform: translateY(-50%);
    background: none;
    border: none;
    font-size: 1.6em;
    cursor: pointer;
    padding: 0 5px;
    color: var(--text-color);
}

.main-container {
    display: flex;
    flex-grow: 1;
    max-width: 1600px;
    width: 95%;
    margin: 15px auto;
    gap: var(--layout-gap);
    padding: 0 10px;
    overflow: hidden; /* Keep this to contain flex children */
    transition: width 260ms ease, gap 260ms ease;
}

/* 左右導航欄樣式 (桌面) */
.side-nav {
    flex: 0 0 var(--side-nav-width);
    width: var(--side-nav-width);
    min-width: 0;
    background-color: var(--nav-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 15px;
    display: flex;
    flex-direction: column;
    max-height: calc(100vh - var(--header-height) - var(--footer-height) - 40px); /* 40px for .main-container margin-top+bottom */
    box-shadow: 0 2px 5px var(--shadow-color);
    overflow: hidden;
    transition:
        flex-basis 260ms ease,
        width 260ms ease,
        padding 260ms ease,
        opacity 180ms ease,
        transform 260ms ease,
        background-color 0.3s ease,
        border-color 0.3s ease;
}

.side-nav h2 {
    text-align: center;
    margin: 0 0 15px 0; /* Use margin shorthand */
    color: var(--header-color);
    font-family: 'Noto Sans SC', sans-serif;
    font-size: 1.3em;
    flex-shrink: 0;
}

.poem-list-container {
    flex-grow: 1;
    overflow-y: auto;
    padding: 0 5px 0 0;
    margin: 0; /* Already removed by global reset */
    scrollbar-width: thin;
    scrollbar-color: var(--scrollbar-thumb) var(--scrollbar-track);
}

.poem-list-container::-webkit-scrollbar { width: 8px; }
.poem-list-container::-webkit-scrollbar-track { background: var(--scrollbar-track); border-radius: 4px; }
.poem-list-container::-webkit-scrollbar-thumb { background-color: var(--scrollbar-thumb); border-radius: 4px; border: 2px solid var(--scrollbar-track); }

/* Base Nav Button Style */
.nav-button {
    display: block;
    width: 100%;
    padding: 10px 8px;
    text-align: left;
    border-bottom: 1px dashed rgba(128, 128, 128, 0.1);
    font-size: 1em;
    border-radius: 5px;
    line-height: 1.5;
    transition: background-color 0.2s ease, color 0.2s ease, box-shadow 0.2s ease;
    /* Inherits button resets like background: none, border: none, font: inherit, color: inherit, cursor: pointer */
    color: var(--text-color); /* Re-apply text color */
}
.nav-button:last-child { border-bottom: none; }

.poem-list-container li,
#mobile-poem-list li {
    margin-bottom: 6px;
}

/* Hover/Active State (Common) */
.nav-button:hover {
    background-color: var(--button-hover-bg);
    color: var(--header-color);
}
.nav-button.active-poem {
    font-weight: bold;
    box-shadow: inset 0 0 0 2px var(--accent-color);
}

/* 已讀標記 — 直接顯示在篇目按鈕上 */
.nav-button.is-achieved {
    border-left: 3px solid #556B2F;
    position: relative;
    padding-right: 30px;
}

.nav-button.is-achieved::after {
    content: '';
    position: absolute;
    right: 6px;
    top: 50%;
    transform: translateY(-50%);
    width: 20px;
    height: 20px;
    background: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 20 20'><circle cx='10' cy='10' r='9' fill='%23556B2F'/><path d='M6 10.2 L8.6 12.8 L14 7.6' fill='none' stroke='white' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round'/></svg>") center/contain no-repeat;
    transition: transform 0.15s ease;
}

.nav-button.is-achieved:hover::after {
    transform: translateY(-50%) scale(1.12);
}

body.dark-mode .nav-button.is-achieved {
    border-left-color: #8bc48b;
}

body.dark-mode .nav-button.is-achieved::after {
    background: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 20 20'><circle cx='10' cy='10' r='9' fill='%23b5d89a'/><path d='M6 10.2 L8.6 12.8 L14 7.6' fill='none' stroke='%231f2b16' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round'/></svg>") center/contain no-repeat;
}

.nav-button.is-achieved.active-poem {
    box-shadow: inset 0 0 0 3px var(--accent-color), 0 8px 20px rgba(80, 70, 60, 0.12);
}

/* --- Conditional Button Styling --- */
.nav-button.has-questions {
    background-color: var(--ghibli-color-fallback, transparent);
    color: #333;
    font-weight: 500;
}
.nav-button.has-questions-color-1 { background-color: var(--ghibli-color-1); }
.nav-button.has-questions-color-2 { background-color: var(--ghibli-color-2); }
.nav-button.has-questions-color-3 { background-color: var(--ghibli-color-3); }
.nav-button.has-questions-color-4 { background-color: var(--ghibli-color-4); }
.nav-button.has-questions-color-5 { background-color: var(--ghibli-color-5); }
.nav-button.has-questions-color-6 { background-color: var(--ghibli-color-6); }

body.dark-mode .nav-button.has-questions {
    color: #eee;
}
.nav-button.has-questions:hover {
    filter: brightness(1.05);
    color: #000;
}
body.dark-mode .nav-button.has-questions:hover {
    filter: brightness(1.1);
    color: #fff;
}

.nav-button.no-questions {
    color: var(--no-question-color);
    font-weight: bold;
}
.nav-button.no-questions:hover {
    background-color: var(--button-hover-bg);
    color: var(--header-color);
}

.scroll-indicator {
    text-align: center;
    font-size: 1em;
    color: var(--text-secondary);
    opacity: 0;
    height: 0;
    overflow: hidden;
    transition: opacity 0.3s ease, height 0.3s ease;
    flex-shrink: 0;
}
.scroll-indicator.visible { opacity: 0.6; height: 1.2em; }

.nav-achievement-summary {
    margin: -6px 0 12px 0;
    padding: 10px 12px;
    border-radius: 10px;
    background: rgba(255, 255, 255, 0.42);
    color: var(--text-secondary);
    font-size: 0.88em;
    line-height: 1.45;
}

body.dark-mode .nav-achievement-summary {
    background: rgba(255, 255, 255, 0.05);
}

.nav-achievement-summary strong {
    display: block;
    color: var(--header-color);
    margin-bottom: 3px;
}

.nav-achievement-summary .sync-state {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    margin-top: 6px;
    font-size: 0.8em;
}

/* 中間內容區 */
#center-content {
    flex: 1 1 auto;
    width: auto;
    background-color: var(--content-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 0;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    font-size: 1.15em;
    box-shadow: 0 2px 8px var(--shadow-color);
    transition:
        background-color 0.3s ease,
        border-color 0.3s ease;
    min-width: 0;
    max-height: calc(100vh - var(--header-height) - var(--footer-height) - 40px);
    overflow-wrap: break-word;
    word-wrap: break-word;
}

#reading-scroll-region {
    flex: 1 1 auto;
    min-height: 0;
    padding: 20px 30px;
    overflow-y: auto;
    scrollbar-width: thin;
    scrollbar-color: var(--scrollbar-thumb) var(--content-bg);
    transition: padding 260ms ease;
}

html.is-reading-focus .main-container {
    width: min(100% - 24px, 1500px);
    gap: 0;
}

html.is-reading-focus .side-nav {
    flex-basis: 0;
    width: 0;
    padding-right: 0;
    padding-left: 0;
    border-right-width: 0;
    border-left-width: 0;
    opacity: 0;
    transform: scale(0.98);
    pointer-events: none;
}

html.is-reading-focus #reading-scroll-region {
    padding-inline: clamp(24px, 7vw, 120px);
}

html.is-reading-focus #placeholder-text,
html.is-reading-focus #poem-display-area {
    width: min(100%, var(--reading-measure));
    max-width: var(--reading-measure);
    margin-inline: auto;
}

html.is-reading-focus .poem-main-text p {
    width: min(100%, 48rem);
    max-width: 48rem;
    font-size: clamp(1.08rem, 0.35vw + 1rem, 1.28rem);
    line-height: 2;
    letter-spacing: 0.025em;
}

html.is-reading-focus .exam-questions {
    width: min(100%, var(--reading-measure));
    margin-inline: auto;
}

#immersive-sequence-nav {
    display: none;
}

html.is-reading-focus #immersive-sequence-nav:not([hidden]) {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
    flex: 0 0 auto;
    align-items: stretch;
    min-height: 64px;
    border-top: 1px solid var(--border-color);
    background: color-mix(in srgb, var(--content-bg) 92%, var(--nav-bg));
}

#immersive-sequence-nav [hidden] {
    display: flex !important;
    visibility: hidden;
    pointer-events: none;
}

.sequence-poem-button {
    position: static;
    display: flex;
    align-items: center;
    gap: 10px;
    width: 100%;
    min-width: 0;
    min-height: 64px;
    padding: 10px clamp(16px, 2.5vw, 34px);
    border: 0;
    border-radius: 0;
    color: var(--text-color);
    background: transparent;
    box-shadow: none;
    opacity: 0.82;
    transition:
        opacity 180ms ease,
        background-color 180ms ease;
}

.sequence-poem-button.previous {
    justify-content: flex-start;
    text-align: left;
}

.sequence-poem-button.next {
    justify-content: flex-end;
    border-left: 1px solid color-mix(in srgb, var(--border-color) 78%, transparent);
    text-align: right;
}

.sequence-poem-button:hover,
.sequence-poem-button:focus-visible {
    opacity: 1;
    background: color-mix(in srgb, var(--button-hover-bg) 64%, transparent);
}

.sequence-poem-button:focus-visible {
    outline: 3px solid color-mix(in srgb, var(--accent-color) 65%, transparent);
    outline-offset: 3px;
}

.sequence-copy {
    min-width: 0;
    display: grid;
    gap: 2px;
}

.sequence-direction {
    color: var(--text-secondary);
    font-family: 'Noto Sans SC', 'BabelStone Han', sans-serif;
    font-size: 0.7rem;
    line-height: 1.2;
    letter-spacing: 0.12em;
}

.sequence-title {
    overflow: hidden;
    color: var(--header-color);
    font-size: 0.92rem;
    font-weight: 700;
    line-height: 1.35;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.sequence-arrow {
    color: var(--accent-color);
    font-family: 'Noto Sans SC', sans-serif;
    font-size: 1.3rem;
    line-height: 1;
    transition: transform 180ms ease;
}

.sequence-poem-button.previous:hover .sequence-arrow,
.sequence-poem-button.previous:focus-visible .sequence-arrow {
    transform: translateX(-3px);
}

.sequence-poem-button.next:hover .sequence-arrow,
.sequence-poem-button.next:focus-visible .sequence-arrow {
    transform: translateX(3px);
}

#reading-scroll-region::-webkit-scrollbar { width: 8px; }
#reading-scroll-region::-webkit-scrollbar-track { background: rgba(0,0,0,0.05); border-radius: 4px; }
#reading-scroll-region::-webkit-scrollbar-thumb { background-color: var(--scrollbar-thumb); border-radius: 4px; border: 2px solid var(--content-bg); }

#placeholder-text {
    text-align: center;
    color: var(--text-secondary);
    padding: 50px 0 20px 0; /* Adjust padding */
    min-height: 200px;
    max-width: 85%;
    margin: 0 auto; /* Re-center with margin */
}
#placeholder-text h2 {
     color: var(--header-color);
     font-size: 1.5em;
     margin-bottom: 20px;
}
#placeholder-text .exam-marker-example {
    font-size: 0.9em;
}
#placeholder-text p { /* Apply general p styles within placeholder */
    line-height: 1.8;
    margin-bottom: 1em;
}
#placeholder-text p:last-of-type {
    margin-top: 15px;
    font-style: italic;
    font-size: 0.95em;
}
#placeholder-text a { /* Style links in placeholder */
    color: var(--accent-color);
    text-decoration: underline;
}
body.dark-mode #placeholder-text a {
    color: #a8c0a0;
}


#poem-display-area {
    text-align: center;
}

/* Styles specifically for the main poem text container */
.poem-main-text h1 {
    font-size: 1.8em;
    color: var(--header-color);
    text-align: center;
    margin: 0 0 15px 0;
    font-weight: bold;
}
.poem-main-text .meta {
    font-size: 0.9em;
    color: var(--text-secondary);
    text-align: center; /* 保留 */
    margin: 0 auto 25px auto; /* 修改: 使用 margin auto 嘗試水平居中塊本身 */
    padding: 0; /* 確保沒有左右 padding 影響 */
    display: block; /* 添加/確認: 確保是塊級 */
    width: fit-content; /* 修改: 讓寬度包裹內容 */
    /* 或者嘗試 width: 100%; 如果 fit-content 不行 */
}
.poem-main-text p {
    text-align: center;
    text-indent: 0;
    line-height: 1.8;
    margin: 0 auto 1.2em auto;
    padding: 0;
    max-width: 85%; /* Narrower text */
    font-weight: bold;
    overflow-wrap: break-word;
    word-wrap: break-word;
}

.inline-pinyin {
    ruby-position: over;
    text-decoration: underline dotted rgba(141, 181, 128, 0.55);
    text-underline-offset: 0.14em;
}

.inline-pinyin rt {
    color: #c62828;
    font-family: 'Noto Sans SC', 'BabelStone Han', sans-serif;
    font-size: 0.58em;
    font-weight: 600;
    line-height: 1;
    letter-spacing: 0;
}

body.dark-mode .inline-pinyin rt {
    color: #ff6b6b;
}

.poem-main-text h1 .inline-pinyin rt {
    font-size: 0.48em;
}

/* Exam Marker Styling */
.exam-marker {
   font-size: 0.75em;
   color: var(--accent-color);
   background-color: rgba(141, 181, 128, 0.15);
   padding: 2px 5px;
   border-radius: 4px;
   margin-left: 6px;
   white-space: nowrap;
   font-family: 'Noto Sans SC', sans-serif;
   vertical-align: baseline;
   display: inline-block;
}
body.dark-mode .exam-marker {
    color: #a8c0a0;
    background-color: rgba(168, 192, 160, 0.2);
}

/* --- Exam Questions Styling --- */
.exam-questions {
    margin-top: 40px;
    padding-top: 20px;
    border-top: 1px dashed var(--border-color);
    text-align: left;
}

.exam-questions h2 {
    text-align: center;
    color: var(--header-color);
    font-size: 1.4em;
    margin: 0 0 25px 0;
    font-family: 'Noto Sans SC', sans-serif;
}

.question-item {
    margin-bottom: 25px;
}

.question-text {
    font-weight: bold;
    color: var(--text-color);
    cursor: pointer;
    line-height: 1.6;
    margin: 0 0 8px 0 !important; /* Use shorthand margin */
    padding: 5px 0 !important;
    text-align: left !important;
    text-indent: 0 !important;
    max-width: 100%;
    overflow-wrap: break-word;
    word-wrap: break-word;
}
.question-text:focus {
     outline: 2px solid var(--accent-color);
     outline-offset: 2px;
     border-radius: 2px;
}

.question-year {
    font-size: 0.85em;
    color: var(--text-secondary);
    font-weight: normal;
    margin-left: 8px;
    white-space: nowrap;
}

.answer {
    margin: 0 0 0 2em; /* Use shorthand margin */
    padding: 10px;
    background-color: rgba(0, 0, 0, 0.03);
    border-radius: 6px;
    color: var(--text-color);
    line-height: 1.7;
    text-align: left !important;
    animation: fadeIn 0.3s ease;
    overflow-wrap: break-word;
    word-wrap: break-word;
}

body.dark-mode .answer {
    background-color: rgba(255, 255, 255, 0.05);
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-5px); }
  to { opacity: 1; transform: translateY(0); }
}

/* AI 聊天界面樣式 - Glassmorphism Update */
#ai-chat-interface {
    position: fixed;
    bottom: 75px;
    right: 15px;
    width: 310px;
    max-height: 400px;
    background-color: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(15px) saturate(150%);
    -webkit-backdrop-filter: blur(15px) saturate(150%);
    border: 1px solid rgba(255, 255, 255, 0.2);
    box-shadow: 0 4px 15px var(--shadow-color);
    border-radius: 15px;
    padding: 12px;
    display: none;
    flex-direction: column;
    z-index: 1000;
    opacity: 0;
    transform: translateY(20px);
    pointer-events: none;
    transition: opacity 0.3s ease, transform 0.3s ease, background-color 0.3s ease, border-color 0.3s ease, width 0.3s ease, height 0.3s ease, bottom 0.3s ease, right 0.3s ease, border-radius 0.3s ease;
}
body.dark-mode #ai-chat-interface {
    background-color: rgba(30, 35, 28, 0.25);
    border: 1px solid rgba(255, 255, 255, 0.1);
}
 #ai-chat-interface.visible {
    display: flex;
    opacity: 1;
    transform: translateY(0);
    pointer-events: auto;
}

#ai-close-btn {
    position: absolute;
    top: 8px;
    right: 8px;
    font-size: 1.3em;
    color: var(--text-secondary);
    line-height: 1;
    z-index: 1001;
    /* Inherits button reset */
    padding: 0; /* Ensure no extra padding */
}
#ai-close-btn:hover { color: var(--text-color); }

#ai-chat-interface h3 {
    text-align: center;
    margin: 0 0 12px 0;
    color: var(--header-color);
    font-family: 'Noto Sans SC', sans-serif;
    font-size: 1.1em;
    flex-shrink: 0;
}

#ai-messages {
    flex-grow: 1;
    overflow-y: auto;
    margin-bottom: 8px;
    padding: 5px;
    scrollbar-width: thin;
    scrollbar-color: var(--scrollbar-thumb) rgba(255, 255, 255, 0.1);
}
body.dark-mode #ai-messages {
     scrollbar-color: var(--scrollbar-thumb) rgba(0, 0, 0, 0.1);
}

#ai-messages::-webkit-scrollbar { width: 6px; }
#ai-messages::-webkit-scrollbar-track { background: rgba(255, 255, 255, 0.1); border-radius: 3px; }
body.dark-mode #ai-messages::-webkit-scrollbar-track { background: rgba(0, 0, 0, 0.1); }
#ai-messages::-webkit-scrollbar-thumb { background-color: var(--scrollbar-thumb); border-radius: 3px; }

#ai-messages .message {
    padding: 7px 11px;
    margin-bottom: 8px;
    border-radius: 16px;
    max-width: 90%;
    word-wrap: break-word;
    line-height: 1.45;
    font-size: 0.9em;
    box-shadow: 0 1px 1px var(--shadow-color);
    color: var(--text-color);
}

#ai-messages .user {
    background-color: rgba(112, 148, 100, 0.7);
    color: white;
    margin-left: auto;
    border-bottom-right-radius: 5px;
}
body.dark-mode #ai-messages .user {
    background-color: rgba(82, 105, 76, 0.8);
    color: var(--text-color);
}

#ai-messages .ai {
    background-color: rgba(232, 232, 224, 0.7);
    color: #333;
    margin-right: auto;
    border-bottom-left-radius: 5px;
}
body.dark-mode #ai-messages .ai {
    background-color: rgba(69, 74, 65, 0.8);
    color: var(--text-color);
}

/* Thinking Indicator Styling */
#ai-messages .message.ai-thinking {
    font-style: italic;
    color: var(--text-secondary);
    text-align: center;
    background-color: transparent;
    padding: 4px;
    font-size: 0.85em;
    box-shadow: none;
    margin: 5px 0; /* Use shorthand margin */
    animation: thinking-pulse 1.5s infinite ease-in-out;
}

@keyframes thinking-pulse {
  0% { opacity: 0.5; }
  50% { opacity: 1; }
  100% { opacity: 0.5; }
}

/* System message styling */
#ai-messages .message.system {
     font-style: italic;
     color: var(--text-secondary);
     text-align: center;
     background-color: transparent;
     padding: 4px;
     font-size: 0.85em;
     box-shadow: none;
     margin: 5px 0;
}
#ai-messages .message.system.info {
     font-size: 0.8em;
     margin-top: -5px;
     background-color: transparent;
}
#ai-messages .message.system.error {
    color: var(--no-question-color);
    font-weight: bold;
    background-color: rgba(192, 57, 43, 0.1);
    border-radius: 4px;
}
body.dark-mode #ai-messages .message.system.error {
     background-color: rgba(231, 76, 60, 0.15);
}

.ai-input-area {
    display: flex;
    gap: 6px;
    margin-top: 5px;
    align-items: flex-end;
    flex-shrink: 0;
}

.ai-input-area textarea {
    flex-grow: 1;
    padding: 8px;
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 6px;
    background-color: rgba(255, 255, 255, 0.3);
    color: var(--text-color);
    font-size: 0.9em;
    font-family: inherit;
    resize: none;
    overflow-y: hidden;
    line-height: 1.4;
    min-height: 38px;
    box-sizing: border-box;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}
body.dark-mode .ai-input-area textarea {
    background-color: rgba(40, 45, 38, 0.6);
    border: 1px solid rgba(255, 255, 255, 0.15);
}

.ai-input-area textarea:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 2px rgba(141, 181, 128, 0.3);
    background-color: rgba(255, 255, 255, 0.5);
}
body.dark-mode .ai-input-area textarea:focus {
     background-color: rgba(40, 45, 38, 0.8);
}

#ai-send-btn {
    padding: 6px 12px;
    background-color: var(--accent-color);
    color: white;
    border-radius: 6px;
    font-size: 0.9em;
    flex-shrink: 0;
    height: 38px;
    transition: background-color 0.2s ease;
     /* Inherits button reset */
     border: none;
     cursor: pointer;
}
#ai-send-btn:hover { background-color: var(--header-color); }

/* Ensure Open AI Button is correctly positioned */
#open-ai-btn {
    position: fixed;
    bottom: 15px;
    right: 15px;
    font-size: 1.8em;
    background-color: var(--accent-color);
    color: white;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    display: flex;
    justify-content: center;
    align-items: center;
    box-shadow: 0 2px 10px var(--shadow-color);
    z-index: 999;
    transition: background-color 0.3s ease, transform 0.2s ease, opacity 0.3s ease;
    opacity: 1;
    /* Inherits button reset */
    padding: 0;
    cursor: pointer;
}
#open-ai-btn:hover {
    background-color: var(--header-color);
    transform: scale(1.1);
}
#open-ai-btn.hidden {
    opacity: 0;
    pointer-events: none;
}
  
  footer {
      text-align: center;
      padding: 8px;
      color: var(--no-question-color); /* Changed footer text color */
      font-size: 0.85em;
      background-color: rgba(255, 255, 255, 0.05);
      backdrop-filter: blur(2px);
      border-top: 1px solid var(--border-color);
      flex-shrink: 0;
      height: var(--footer-height);
      box-sizing: border-box;
  }
  footer p { /* Target the paragraph for margin reset */
      margin: 0;
  }
  footer a {
      color: var(--no-question-color); /* Match footer text color */
      /* text-decoration: none; /* Inherited from global reset */
   }
  footer a:hover {
      text-decoration: underline;
      filter: brightness(0.9);
  }
  body.dark-mode footer a {
       color: var(--no-question-color);
  }
  
/* --- Mobile Navigation Styles (Global - Initial State) --- */
#mobile-menu-toggle {
    display: none;
    font-size: 1.8em;
    color: var(--text-color);
    padding: 5px;
    line-height: 1;
    z-index: 1101;
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    left: 15px;
    /* Inherits button reset */
}
    
    .mobile-nav {
        display: none;
        position: fixed;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background-color: rgba(0, 0, 0, 0.7);
        z-index: 1100;
        opacity: 0;
        transition: opacity 0.3s ease;
        backdrop-filter: blur(5px);
    }
    .mobile-nav.visible { display: block; opacity: 1; }
    
    .mobile-nav-content {
        position: absolute;
        top: 50%;
        left: 50%;
        transform: translate(-50%, -50%) scale(0.95);
        background-color: var(--nav-bg);
        padding: 35px 15px 15px 15px;
        border-radius: 10px;
        max-height: 85vh;
        width: 90%;
        max-width: 450px;
        display: flex;
        flex-direction: column;
        box-shadow: 0 5px 15px rgba(0,0,0,0.2);
        opacity: 0;
        transition: opacity 0.2s 0.1s ease, transform 0.2s 0.1s ease;
    }
    .mobile-nav.visible .mobile-nav-content { opacity: 1; transform: translate(-50%, -50%) scale(1); }
    
    .mobile-nav-content h2 {
        text-align: center;
        color: var(--header-color);
        margin: 0 0 12px 0;
        font-size: 1.3em;
        flex-shrink: 0;
    }
    
    #mobile-poem-list {
        flex-grow: 1;
        overflow-y: auto;
        /* list-style: none; Inherited */
        padding: 0;
        margin: 0;
        scrollbar-width: thin;
        scrollbar-color: var(--scrollbar-thumb) var(--nav-bg);
    }
    #mobile-poem-list::-webkit-scrollbar { width: 6px; }
    #mobile-poem-list::-webkit-scrollbar-track { background: rgba(0,0,0,0.05); border-radius: 3px; }
    #mobile-poem-list::-webkit-scrollbar-thumb { background-color: var(--scrollbar-thumb); border-radius: 3px; }
    
    #mobile-poem-list .nav-button {
        padding: 11px 8px;
        font-size: 0.95em;
    }
    #mobile-poem-list .nav-button:last-child { border-bottom: none; }
    #mobile-poem-list .nav-button:hover { background-color: var(--button-hover-bg); color: var(--header-color); }
    
    #mobile-poem-list .nav-button.has-questions {
        background-color: var(--ghibli-color-fallback, transparent);
        color: #333;
        font-weight: 500;
    }
    body.dark-mode #mobile-poem-list .nav-button.has-questions {
         color: #eee;
    }
    #mobile-poem-list .nav-button.has-questions-color-1 { background-color: var(--ghibli-color-1); }
    #mobile-poem-list .nav-button.has-questions-color-2 { background-color: var(--ghibli-color-2); }
    #mobile-poem-list .nav-button.has-questions-color-3 { background-color: var(--ghibli-color-3); }
    #mobile-poem-list .nav-button.has-questions-color-4 { background-color: var(--ghibli-color-4); }
    #mobile-poem-list .nav-button.has-questions-color-5 { background-color: var(--ghibli-color-5); }
    #mobile-poem-list .nav-button.has-questions-color-6 { background-color: var(--ghibli-color-6); }
    
    #mobile-poem-list .nav-button.no-questions {
        color: var(--no-question-color);
        font-weight: bold;
    }
    #mobile-poem-list .nav-button.active-poem {
        background-color: var(--accent-color);
        color: white;
        font-weight: bold;
        box-shadow: none;
    }
    #mobile-poem-list .nav-button.has-questions.active-poem {
         box-shadow: inset 0 0 0 3px rgba(255, 255, 255, 0.7);
         background-color: var(--accent-color);
         color: white;
    }
    body.dark-mode #mobile-poem-list .nav-button.has-questions.active-poem {
         box-shadow: inset 0 0 0 3px rgba(0, 0, 0, 0.4);
    }

    .mobile-nav-content .nav-achievement-summary {
        margin: 0 0 12px 0;
    }
    
    #mobile-nav-close {
        position: absolute;
        top: 8px;
        right: 8px;
        font-size: 1.8em;
        color: var(--text-secondary);
        line-height: 1;
        padding: 5px;
        /* Inherits button reset */
    }
    #mobile-nav-close:hover { color: var(--text-color); }
    
/* --- Responsive Design Adjustments --- */

/* Tablet Styles (e.g., 801px to 1024px) - Keep sidebars visible, adjust layout */
@media (max-width: 1024px) {
    .main-container {
        width: 98%;
    }
    .side-nav {
        padding: 12px;
    }
    #center-content {
        font-size: 1.1em;
    }
    #reading-scroll-region { padding: 15px 25px; }
    #main-title { font-size: 1.5em; }
    #dark-mode-toggle { font-size: 1.5em; right: 15px; }
    /* #mobile-menu-toggle { display: none; } /* Removed redundant rule */
}

/* Smaller Tablets and Large Phones (e.g., <= 800px) - Hide sidebars, show mobile toggle */
@media (max-width: 800px) {
    header { padding: 6px 15px; height: calc(var(--header-height) - 4px); }
    footer { padding: 6px; height: calc(var(--footer-height) - 4px); }
    #main-title { font-size: 1.4em; }
    #dark-mode-toggle { font-size: 1.4em; right: 10px; }
    #reading-mode-toggle { display: none; }
    #immersive-sequence-nav { display: none !important; }

    #mobile-menu-toggle {
        display: block; /* Show the button */
        font-size: 1.6em;
        position: absolute;
        top: 50%;
        left: 10px;
        transform: translateY(-50%);
    }

    .main-container {
        flex-direction: column;
        width: 100%;
        padding: 0 5px;
        margin: 8px auto 10px auto;
        gap: 10px;
        overflow: visible;
    }
    .side-nav {
        display: none; /* Hide sidebars */
    }

    #center-content {
        width: auto;
        order: 0;
        margin: 0;
        flex-grow: 1;
        min-height: 300px;
        padding: 0;
        font-size: 1.05em;
        max-height: none;
        overflow: visible;
        overflow-wrap: break-word;
        word-wrap: break-word;
    }
     #reading-scroll-region {
        padding: 15px;
        overflow-y: visible;
     }
     #placeholder-text { max-width: 90%; }
     .poem-main-text p { max-width: 90%; }

     /* --- Mobile AI Fullscreen --- */
      #ai-chat-interface.visible {
          width: 100%;
          height: 100%; /* Cover full height */
          bottom: 0;
          right: 0;
          border-radius: 0;
          max-height: none;
          background-color: rgba(244, 241, 233, 0.88); /* Slightly less transparent */
          backdrop-filter: blur(10px) saturate(120%);
          -webkit-backdrop-filter: blur(10px) saturate(120%);
          z-index: 1200;
          padding: 15px;
          box-sizing: border-box;
      }
      body.dark-mode #ai-chat-interface.visible {
          background-color: rgba(58, 63, 55, 0.9); /* Darker BG for mobile */
      }
      #ai-chat-interface.visible #ai-close-btn {
          font-size: 1.8em;
          top: 15px;
          right: 15px;
          color: var(--text-color);
      }
      #ai-chat-interface.visible #ai-messages {
          padding: 10px;
          margin-bottom: 10px; /* Increase spacing */
      }
      #ai-chat-interface.visible .ai-input-area {
          padding: 0 10px 10px 10px;
          background: transparent;
      }
      /* #open-ai-btn.hidden handled by JS */
}

@media (prefers-reduced-motion: reduce) {
    .main-container,
    .side-nav,
    #center-content,
    #reading-scroll-region,
    #reading-mode-toggle,
    .sequence-poem-button,
    .sequence-arrow {
        transition: none;
    }
}

/* Mobile Phones (e.g., <= 600px) - Further adjustments */
 @media (max-width: 600px) {
     #main-title { font-size: 1.2em; }
     #dark-mode-toggle { font-size: 1.4em; }
     #mobile-menu-toggle { font-size: 1.5em; }

     .mobile-nav-content { width: 95%; padding: 30px 10px 10px 10px; }
     #mobile-poem-list .nav-button { padding: 9px 5px; font-size: 0.9em; }

     .main-container { margin: 5px auto 8px auto; gap: 8px; }
     #center-content { font-size: 1em; min-height: 150px; }
     #reading-scroll-region { padding: 10px; }
     .poem-main-text h1 { font-size: 1.4em; }
     .poem-main-text .meta { font-size: 0.85em; margin-bottom: 15px; }
     .poem-main-text p { line-height: 1.8; margin-bottom: 1.2em; font-size: 1em; max-width: 95%; }
     #placeholder-text { max-width: 95%; }
     .exam-questions h2 { font-size: 1.1em; margin-bottom: 15px; }
     .question-item { margin-bottom: 15px; }
     .answer { margin-left: 0.8em; padding: 8px; }

     #open-ai-btn { width: 45px; height: 45px; font-size: 1.6em; bottom: 10px; right: 10px; }
     /* AI Fullscreen already handled by max-width: 800px */
     #ai-chat-interface.visible { padding: 10px; } /* Adjust padding if needed */

     footer { font-size: 0.8em; }
 }