:root {
    --known-color: #2ecc71;
    --unknown-color: #e74c3c;
    --primary-color: #3498db;
    --danger-color: #c0392b;
    --bg-color: #f4f7f9;
    --card-bg: #ffffff;
    --text-color: #2c3e50;
    --border-color: #e0e0e0;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    overscroll-behavior: none;
}

#app-container {
    display: flex;
    flex-direction: column;
    width: 100%;
    max-width: 1200px;
    height: 100vh;
    margin: 0 auto;
    background: var(--card-bg);
    box-shadow: 0 0 20px rgba(0,0,0,0.1);
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 20px;
    border-bottom: 1px solid var(--border-color);
    flex-shrink: 0;
}

.mode-switcher {
    display: flex;
    background: var(--bg-color);
    border-radius: 8px;
    padding: 4px;
}
.mode-switcher button {
    border: none;
    padding: 8px 15px;
    border-radius: 6px;
    cursor: pointer;
    background: transparent;
    font-weight: 600;
    color: #7f8c8d;
    transition: all 0.3s ease;
}
.mode-switcher button.active {
    background: var(--card-bg);
    color: var(--primary-color);
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 10px;
}

#download-btn {
    background: none;
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
    padding: 6px 12px;
    border-radius: 5px;
    cursor: pointer;
    font-size: 0.9em;
}

#reset-btn {
    background: none;
    border: none;
    font-size: 1.5em;
    cursor: pointer;
    color: #7f8c8d;
    padding: 0 5px;
}

.view {
    display: none;
    flex-grow: 1;
    flex-direction: column;
    overflow: hidden;
}
.view.active {
    display: flex;
}

/* --- 集中モード --- */
#focus-view { padding: 20px; }
.progress-stats { margin-bottom: 20px; }
.progress-bar-container { width: 100%; height: 8px; background-color: var(--border-color); border-radius: 4px; overflow: hidden; margin-bottom: 10px; }
#progress-bar { width: 0%; height: 100%; background-color: var(--primary-color); transition: width 0.3s ease; }
#counter { text-align: center; display: block; color: #555; }
#card-area { perspective: 1000px; flex-grow: 1; display: flex; align-items: center; justify-content: center; }
#word-card-focus { width: 100%; max-width: 350px; height: 95%; background: var(--card-bg); border-radius: 12px; border: 1px solid var(--border-color); padding: 25px; box-sizing: border-box; display: flex; flex-direction: column; justify-content: center; text-align: center; transition: transform 0.3s ease, opacity 0.3s ease; }
#word-card-focus.exit-left { transform: translateX(-150%) rotate(-15deg); opacity: 0; }
#word-card-focus.exit-right { transform: translateX(150%) rotate(15deg); opacity: 0; }
#word-card-focus h2 { font-size: 2.2em; margin: 0 0 5px; }
#word-card-focus .pronunciation { font-size: 1em; color: #7f8c8d; margin-bottom: 15px; }
.controls { display: flex; gap: 10px; margin-top: 20px; }
.control-btn { flex: 1; padding: 15px; font-size: 1.1em; font-weight: bold; border: none; border-radius: 8px; cursor: pointer; color: #fff; display: flex; justify-content: center; align-items: center; gap: 8px; transition: background-color 0.2s, opacity 0.2s; }
.undo-btn { flex: 0 1 auto; padding: 0 20px; background-color: #7f8c8d; }
.undo-btn:disabled { opacity: 0.5; cursor: not-allowed; }
.known-btn { background-color: var(--known-color); }
.unknown-btn { background-color: var(--unknown-color); }
.key-hint { display: inline-block; border: 1px solid rgba(255,255,255,0.5); padding: 2px 6px; border-radius: 4px; font-size: 0.8em; }

/* --- 一覧モード --- */
#review-view { padding: 20px; }
.review-columns { display: flex; gap: 20px; height: 100%; }
.column { flex: 1; display: flex; flex-direction: column; overflow: hidden; border: 1px solid var(--border-color); border-radius: 8px; }
.column-header { padding: 10px; border-bottom: 1px solid var(--border-color); flex-shrink: 0; }
.column-header h3 { margin: 0 0 10px; text-align: center; }
.column-header input { width: 100%; padding: 8px; border: 1px solid var(--border-color); border-radius: 4px; box-sizing: border-box; }
.list-container { flex-grow: 1; overflow-y: auto; }
.list-item { border-bottom: 1px solid var(--border-color); }
.list-item:last-child { border-bottom: none; }
.item-summary { display: flex; justify-content: space-between; align-items: center; padding: 12px 10px; cursor: pointer; }
.item-summary:hover { background-color: #f9f9f9; }
.item-summary .word { font-weight: 600; }
.item-details { display: none; padding: 10px 15px 15px; background-color: #fdfdfd; border-top: 1px solid var(--border-color); }
.item-details p { margin: 0 0 8px; }
.item-details .pronunciation { font-size: 0.9em; color: #7f8c8d; }
.item-details .weblio { font-size: 1em; color: #333; word-break: break-word; }
.item-details .level { font-size: 0.8em; color: #7f8c8d; text-align: right; margin: 5px 0 0; }
.list-item.expanded > .item-details { display: block; }
.move-btn { cursor: pointer; background: none; border: 1px solid #aaa; border-radius: 50%; width: 24px; height: 24px; font-weight: bold; flex-shrink: 0; margin-left: 10px; }

/* --- カードモード --- */
#grid-view { overflow-y: auto; padding: 20px; }
#card-grid-container { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 20px; }
.grid-card {
    background: var(--card-bg);
    border: 2px solid var(--border-color); /* 枠線の太さを変更 */
    border-radius: 8px;
    padding: 15px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.05);
    display: flex;
    flex-direction: column;
    transition: border-color 0.3s ease; /* 色が変わる際のアニメーション */
}
.grid-card h3 { margin: 0 0 5px; font-size: 1.5em; text-align: center; }
.grid-card .pronunciation { font-size: 0.9em; color: #7f8c8d; text-align: center; display: block; margin-bottom: 15px; }
.grid-card-details { border-top: 1px solid var(--border-color); border-bottom: 1px solid var(--border-color); padding: 10px 0; margin: 10px 0; flex-grow: 1; }
.grid-card .weblio { font-size: 0.95em; color: #333; display: block; max-height: 80px; overflow-y: auto; padding-right: 5px; }
.grid-card .level { font-size: 0.8em; color: #7f8c8d; text-align: right; }
.toggle-switch-container { display: flex; align-items: center; justify-content: center; margin-top: 15px; border-top: 1px solid var(--border-color); padding-top: 15px; flex-shrink: 0; }
.toggle-switch { position: relative; display: inline-block; width: 50px; height: 28px; }
.toggle-switch input { opacity: 0; width: 0; height: 0; }
.slider { position: absolute; cursor: pointer; top: 0; left: 0; right: 0; bottom: 0; background-color: var(--unknown-color); transition: .4s; border-radius: 28px; }
.slider:before { position: absolute; content: ""; height: 20px; width: 20px; left: 4px; bottom: 4px; background-color: white; transition: .4s; border-radius: 50%; }
input:checked + .slider { background-color: var(--known-color); }
input:checked + .slider:before { transform: translateX(22px); }
.toggle-label-text { margin-left: 10px; font-weight: bold; width: 100px; }
.toggle-label-text.known { color: var(--known-color); }
.toggle-label-text.unknown { color: var(--unknown-color); }

/* --- 単語カラーリング --- */
.colored-word { padding-bottom: 2px; border-bottom: 3px solid; }

/* --- モーダル --- */
#modal-overlay { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0, 0, 0, 0.5); display: flex; justify-content: center; align-items: center; z-index: 1000; opacity: 1; transition: opacity 0.3s ease; }
#modal-overlay.hidden { opacity: 0; pointer-events: none; }
#modal-content { background: #fff; padding: 30px; border-radius: 8px; max-width: 400px; width: 90%; text-align: center; box-shadow: 0 5px 15px rgba(0,0,0,0.3); }
.modal-actions { margin-top: 20px; display: flex; justify-content: center; gap: 15px; }
.modal-actions button { padding: 10px 20px; border-radius: 5px; border: none; font-weight: bold; cursor: pointer; }
.modal-actions .danger { background-color: var(--danger-color); color: #fff; }