/* =========================================================
   STUDY.CSS – Đợt 3b: Công cụ học tập AI
   Ngăn kéo "Học tập": Tóm tắt / Quiz / Flashcard / Hỏi AI.
   Tái dùng khung .rd-drawer/.rd-tabs/.rd-chip... của marks.css.
   ========================================================= */

/* ngăn kéo học tập rộng hơn chút cho dễ đọc */
.rd-drawer.rd-study { width: min(440px, 94vw); }
@media (max-width: 820px) { .rd-drawer.rd-study { width: 100%; } }

/* nút sinh nội dung AI */
.rd-st-ai { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; margin-bottom: 12px; }
.rd-st-aibtn {
  border: 1px solid var(--brand); background: var(--brand); color: #fff;
  border-radius: 9px; padding: 8px 14px; font-size: 13px; font-weight: 700; cursor: pointer;
  display: inline-flex; align-items: center; gap: 6px; font-family: var(--font-sans);
}
.rd-st-aibtn:hover { background: var(--brand-2); }
.rd-st-aibtn:disabled { opacity: .55; cursor: default; }
.rd-st-aibtn.ghost { background: transparent; color: var(--brand); }
.rd-st-aibtn.ghost:hover { background: var(--bg-2); }
.rd-st-note { font-size: 12px; color: var(--ink-soft); }

/* thẻ giới thiệu (chưa tạo nội dung) */
.rd-st-intro { text-align: center; padding: 30px 16px; }
.rd-st-intro__ic { font-size: 36px; line-height: 1; }
.rd-st-intro h4 { margin: 12px 0 4px; color: var(--brand); font-size: 16px; font-family: var(--font-sans); }
.rd-st-intro p { margin: 0 auto 16px; font-size: 13px; color: var(--ink-soft); line-height: 1.55; max-width: 320px; }

/* trạng thái tải / lỗi */
.rd-st-loading { text-align: center; color: var(--ink-soft); font-size: 14px; padding: 26px 10px; }
.rd-spin { display: inline-block; width: 26px; height: 26px; border: 3px solid var(--border); border-top-color: var(--brand); border-radius: 50%; animation: rd-spin 0.8s linear infinite; margin-bottom: 8px; }
@keyframes rd-spin { to { transform: rotate(360deg); } }
.rd-st-err { background: #fdeee4; color: #b45309; border: 1px solid #f0c8a8; border-radius: 9px; padding: 10px 12px; font-size: 13px; margin: 8px 0; }

/* ----- TÓM TẮT ----- */
.rd-sum__sec { margin-bottom: 14px; }
.rd-sum__lb { display: flex; align-items: center; gap: 6px; font-family: var(--font-sans); font-weight: 800; font-size: 13px; color: var(--brand); margin-bottom: 5px; text-transform: uppercase; letter-spacing: .3px; }
.rd-sum__sec p { margin: 0; font-size: 14.5px; line-height: 1.6; }
.rd-sum__sec ul { margin: 0; padding-left: 20px; }
.rd-sum__sec li { font-size: 14px; line-height: 1.55; margin: 4px 0; }
.rd-sum__q { background: var(--accent-soft); border-left: 3px solid var(--accent); border-radius: 0 9px 9px 0; padding: 10px 12px; font-style: italic; }

/* ----- QUIZ ----- */
.rd-qz__item { border: 1px solid var(--border); border-radius: 12px; padding: 12px; margin-bottom: 12px; background: var(--bg-2); }
.rd-qz__q { font-weight: 700; font-size: 14.5px; line-height: 1.5; margin-bottom: 9px; }
.rd-qz__q span { color: var(--brand); }
.rd-qz__opt {
  display: block; width: 100%; text-align: left; border: 1px solid var(--border);
  background: var(--paper); color: var(--ink); border-radius: 9px; padding: 9px 12px; margin: 6px 0;
  font-size: 14px; line-height: 1.45; cursor: pointer; font-family: var(--font-sans); transition: background .12s, border-color .12s;
}
.rd-qz__opt:hover { background: var(--bg-2); }
.rd-qz__opt.sel { border-color: var(--brand); background: var(--brand-soft); }
.rd-qz__opt.correct { border-color: #15803d; background: #dcfce7; color: #14532d; }
.rd-qz__opt.wrong { border-color: #b91c1c; background: #fee2e2; color: #7f1d1d; }
.rd-qz__opt.locked { cursor: default; }
.rd-qz__exp { font-size: 13px; color: var(--ink-soft); margin-top: 6px; padding: 8px 10px; background: var(--paper); border-radius: 8px; border-left: 3px solid var(--brand); display: none; }
.rd-qz__exp.show { display: block; }
.rd-qz__score { text-align: center; font-size: 16px; font-weight: 800; color: var(--brand); padding: 12px; background: var(--brand-soft); border-radius: 12px; margin-bottom: 12px; }
.rd-qz__bar { display: flex; gap: 8px; }
.rd-qz__bar .rd-chip { flex: 1; justify-content: center; }

/* ----- FLASHCARD ----- */
.rd-fc-wrap { text-align: center; }
.rd-fc { perspective: 1200px; margin: 6px 0 12px; }
.rd-fc__inner { position: relative; transform-style: preserve-3d; transition: transform .5s; min-height: 210px; cursor: pointer; }
.rd-fc.flip .rd-fc__inner { transform: rotateY(180deg); }
.rd-fc__face {
  position: absolute; inset: 0; backface-visibility: hidden; -webkit-backface-visibility: hidden;
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 8px;
  border: 1px solid var(--border); border-radius: 16px; padding: 20px; box-shadow: var(--shadow-sm);
}
.rd-fc__front { background: linear-gradient(135deg, var(--brand-soft), var(--paper)); }
.rd-fc__back { background: linear-gradient(135deg, #e9f6ee, var(--paper)); transform: rotateY(180deg); }
.rd-fc__tag { font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: .4px; color: var(--ink-soft); }
.rd-fc__txt { font-size: 16px; line-height: 1.5; }
.rd-fc__front .rd-fc__txt { font-weight: 700; }
.rd-fc__hint { font-size: 11px; color: var(--ink-soft); }
.rd-fc-nav { display: flex; align-items: center; justify-content: center; gap: 12px; }
.rd-fc-nav button { width: 40px; height: 40px; border-radius: 50%; border: 1px solid var(--border); background: var(--paper); color: var(--ink); cursor: pointer; font-size: 18px; }
.rd-fc-nav button:hover { background: var(--bg-2); }
.rd-fc-count { font-size: 13px; color: var(--ink-soft); min-width: 54px; }

/* ----- HỎI AI (chat) ----- */
.rd-chat { display: flex; flex-direction: column; height: 100%; }
.rd-chat__list { flex: 1; overflow: auto; display: flex; flex-direction: column; gap: 10px; padding: 4px 0 10px; }
.rd-msg { max-width: 86%; padding: 9px 12px; border-radius: 14px; font-size: 14px; line-height: 1.5; white-space: pre-wrap; }
.rd-msg.user { align-self: flex-end; background: var(--brand); color: #fff; border-bottom-right-radius: 4px; }
.rd-msg.ai { align-self: flex-start; background: var(--bg-2); color: var(--ink); border: 1px solid var(--border); border-bottom-left-radius: 4px; }
.rd-msg.ai.think { color: var(--ink-soft); font-style: italic; }
.rd-chat__sugg { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 8px; }
.rd-chat__sugg .rd-chip { font-size: 12px; }
.rd-chat__in { display: flex; gap: 8px; align-items: flex-end; border-top: 1px solid var(--border); padding-top: 10px; }
.rd-chat__in textarea { flex: 1; resize: none; border: 1px solid var(--border); border-radius: 10px; padding: 9px 11px; font: inherit; font-size: 14px; max-height: 110px; background: var(--paper); color: var(--ink); }
.rd-chat__send { width: 42px; height: 42px; flex: 0 0 auto; border-radius: 10px; border: 0; background: var(--brand); color: #fff; cursor: pointer; display: inline-flex; align-items: center; justify-content: center; }
.rd-chat__send:hover { background: var(--brand-2); }
.rd-chat__send:disabled { opacity: .5; cursor: default; }
.rd-chat__send svg { width: 20px; height: 20px; stroke: currentColor; fill: none; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }

/* khi mở tab Hỏi AI, body ngăn kéo cần chiếm hết chiều cao để chat co giãn */
.rd-drawer.rd-study .rd-drawer__body.chatmode { display: flex; flex-direction: column; overflow: hidden; }
.rd-drawer.rd-study .rd-drawer__body.chatmode .rd-st-view { flex: 1; min-height: 0; display: flex; flex-direction: column; }
.rd-drawer.rd-study .rd-drawer__body.chatmode .rd-chat { flex: 1; min-height: 0; }