/* Lớp học AI — giao diện một trang, ưu tiên điện thoại (bám phong cách app Agent SEE) */
:root {
  --muc: #0f3d5c; --nhan: #0a84ff; --xanh-la: #1f9d55; --do: #d64545; --vang: #b45309;
  --nen: #f2f4f7; --the: #ffffff; --vien: #dde4ec; --chu: #1c2733; --chu-mo: #5a6b7c;
}
* { box-sizing: border-box; margin: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 15.5px; line-height: 1.6; background: var(--nen); color: var(--chu);
  min-height: 100vh; display: flex; flex-direction: column;
}
#dau {
  position: sticky; top: 0; z-index: 10; background: var(--muc); color: #fff;
  padding: 10px 16px; display: flex; justify-content: space-between; align-items: center;
}
.logo { color: #fff; text-decoration: none; font-weight: 800; font-size: 16px; white-space: nowrap; }
@media (max-width: 620px) { .logo span { display: none; } }
.logo span { font-weight: 400; opacity: .8; font-size: 13px; }
#dau-phai { font-size: 13.5px; display: flex; gap: 10px; align-items: center; }
#dau-phai a, #dau-phai button { color: #fff; background: none; border: 1px solid rgba(255,255,255,.4);
  border-radius: 8px; padding: 4px 10px; font-size: 13px; cursor: pointer; text-decoration: none; }
main { flex: 1; width: 100%; max-width: 760px; margin: 0 auto; padding: 16px 14px 40px; }
#chan { text-align: center; font-size: 12.5px; color: var(--chu-mo); padding: 14px; }
#chan a { color: var(--chu-mo); }

h1 { font-size: 22px; color: var(--muc); margin: 10px 0; line-height: 1.35; }
h2 { font-size: 18px; color: var(--muc); margin: 18px 0 8px; }
.mo { color: var(--chu-mo); font-size: 13.5px; }

.the { background: var(--the); border: 1px solid var(--vien); border-radius: 14px;
  padding: 14px 16px; margin: 10px 0; }
.the.khoa { opacity: .55; }
.the-bai { display: flex; justify-content: space-between; align-items: center; gap: 10px;
  cursor: pointer; transition: transform .08s; }
.the-bai:active { transform: scale(.985); }
.nhan-tuan { display: inline-block; font-size: 12px; font-weight: 700; border-radius: 6px;
  padding: 1px 8px; margin-left: 8px; vertical-align: 2px; }
.nhan-tuan.xong { background: #e3f6ea; color: var(--xanh-la); }
.nhan-tuan.dang_hoc { background: #e5f0ff; color: var(--nhan); }
.nhan-tuan.khoa { background: #eef1f5; color: var(--chu-mo); }
.hieu { font-size: 12.5px; color: var(--chu-mo); }
.mien-phi { color: var(--xanh-la); font-weight: 700; font-size: 12px; }
.tien-trinh { height: 6px; background: var(--nen); border-radius: 3px; margin-top: 8px; overflow: hidden; }
.tien-trinh i { display: block; height: 100%; background: var(--nhan); border-radius: 3px; }

button.chinh, a.chinh { display: inline-block; background: var(--nhan); color: #fff; border: none;
  border-radius: 10px; padding: 10px 18px; font-size: 15px; font-weight: 600; cursor: pointer;
  text-decoration: none; }
button.phu { background: #fff; color: var(--muc); border: 1px solid var(--vien); border-radius: 10px;
  padding: 8px 14px; font-size: 14px; cursor: pointer; }
button:disabled { opacity: .5; cursor: default; }

/* bài đọc */
.bai-doc { background: var(--the); border: 1px solid var(--vien); border-radius: 14px; padding: 4px 18px 14px; }
.bai-doc h2, .bai-doc h3, .bai-doc h4 { color: var(--muc); margin: 16px 0 6px; }
.bai-doc p { text-align: justify; margin: 8px 0; }
.bai-doc blockquote { border-left: 4px solid var(--nhan); background: #f7fafd; padding: 8px 12px;
  margin: 10px 0; border-radius: 0 8px 8px 0; font-style: italic; }
.bai-doc ul { padding-left: 20px; } .bai-doc li { margin: 4px 0; text-align: justify; }
.bang-cuon { overflow-x: auto; margin: 10px 0; }
.bai-doc table { border-collapse: collapse; font-size: 13px; min-width: 420px; }
.bai-doc th { background: var(--muc); color: #fff; padding: 5px 8px; text-align: left; }
.bai-doc td { border: 1px solid var(--vien); padding: 5px 8px; vertical-align: top; }
.ghi-video { background: #fff8ec; border: 1px dashed var(--vang); color: var(--vang);
  border-radius: 10px; padding: 8px 12px; font-size: 13.5px; margin: 10px 0; }

/* câu hỏi */
.cau { background: var(--the); border: 1px solid var(--vien); border-radius: 14px; padding: 16px; margin: 12px 0; }
.loi-nhan { background: #f0f6ff; border-radius: 10px; padding: 10px 12px; font-size: 14px;
  color: var(--muc); margin-bottom: 10px; }
.loi-nhan::before { content: "💬 Lời thầy: "; font-weight: 700; }
.cau .de { font-weight: 600; margin-bottom: 10px; }
.lui-cau { margin-top: 14px; padding-top: 12px; border-top: 1px solid var(--vien); }
.pa { display: block; width: 100%; text-align: left; background: #fff; border: 1.5px solid var(--vien);
  border-radius: 10px; padding: 10px 12px; margin: 6px 0; font-size: 14.5px; cursor: pointer; }
.pa.chon { border-color: var(--nhan); background: #f0f6ff; }
.pa.dung { border-color: var(--xanh-la); background: #e3f6ea; }
.pa.sai { border-color: var(--do); background: #fdeaea; }
.ket-qua { border-radius: 10px; padding: 10px 12px; margin-top: 10px; font-size: 14px; }
.ket-qua.dung { background: #e3f6ea; color: #14532d; }
.ket-qua.sai { background: #fdeaea; color: #7f1d1d; }
.ket-qua.cho { background: #fff8ec; color: var(--vang); }
.sx-manh { user-select: none; }
input[type=text], input[type=email], input[type=password], textarea {
  width: 100%; border: 1.5px solid var(--vien); border-radius: 10px; padding: 10px 12px;
  font-size: 15px; font-family: inherit; margin: 6px 0; background: #fff;
}
textarea { min-height: 110px; }
.bang-kiem-xem { background: #f7fafd; border: 1px solid var(--vien); border-radius: 10px;
  padding: 10px 12px; font-size: 13.5px; margin: 8px 0; }
.bang-kiem-xem b { color: var(--muc); }

.thanh-cau { display: flex; gap: 5px; flex-wrap: wrap; margin: 10px 0; }
.thanh-cau i { width: 26px; height: 8px; border-radius: 4px; background: var(--vien); }
.thanh-cau i.dung { background: var(--xanh-la); }
.thanh-cau i.sai { background: var(--do); }
.thanh-cau i.cho { background: var(--vang); }
.thanh-cau i.hien { outline: 2px solid var(--nhan); outline-offset: 1px; }

.hang-thongke { display: flex; gap: 10px; flex-wrap: wrap; margin: 12px 0; }
.o-thongke { flex: 1; min-width: 100px; background: var(--the); border: 1px solid var(--vien);
  border-radius: 12px; padding: 10px; text-align: center; }
.o-thongke b { display: block; font-size: 20px; color: var(--muc); }
.o-thongke span { font-size: 12px; color: var(--chu-mo); }
.huy-hieu { display: inline-block; background: linear-gradient(135deg, #fef3c7, #fde68a);
  border: 1px solid #f59e0b; color: #92400e; border-radius: 999px; padding: 4px 12px;
  font-size: 13px; font-weight: 700; margin: 3px 4px 3px 0; }

#thong-bao { position: fixed; bottom: 20px; left: 50%; transform: translateX(-50%);
  z-index: 50; display: flex; flex-direction: column; gap: 8px; width: min(92vw, 420px); }
.tb { background: var(--muc); color: #fff; border-radius: 12px; padding: 10px 14px;
  font-size: 14px; box-shadow: 0 6px 24px rgba(0,0,0,.25); animation: hien .25s; }
.tb.loi { background: var(--do); }
@keyframes hien { from { opacity: 0; transform: translateY(8px); } }
.trong { text-align: center; color: var(--chu-mo); padding: 30px 10px; }
.xh-hang { display: flex; justify-content: space-between; padding: 6px 2px; border-bottom: 1px solid var(--nen); font-size: 14px; }
.hoi-o { border-top: 1px solid var(--nen); padding: 8px 0; font-size: 14px; }
.hoi-o .tl { background: #f0f6ff; border-radius: 8px; padding: 6px 10px; margin-top: 4px; }
@media (min-width: 700px) { h1 { font-size: 26px; } }

/* thẻ học từng bước (Agent SEE, không video) */
.the-hoc { }
.bai-doc-long h2, .bai-doc-long h3, .bai-doc-long h4 { color: var(--muc); margin: 12px 0 6px; font-size: 16px; }
.bai-doc-long p { text-align: justify; margin: 8px 0; }
.bai-doc-long blockquote { border-left: 4px solid var(--nhan); background: #f7fafd; padding: 8px 12px;
  margin: 10px 0; border-radius: 0 8px 8px 0; font-style: italic; }
.bai-doc-long ul { padding-left: 20px; } .bai-doc-long li { margin: 4px 0; text-align: justify; }
.bai-doc-long table { border-collapse: collapse; font-size: 13px; min-width: 420px; }
.bai-doc-long th { background: var(--muc); color: #fff; padding: 5px 8px; text-align: left; }
.bai-doc-long td { border: 1px solid var(--vien); padding: 5px 8px; vertical-align: top; }

.logo img { height: 30px; width: auto; vertical-align: middle; border-radius: 6px; margin-right: 6px; }
.ve-nha { font-size: 14px; padding: 5px 10px; border: 1px solid rgba(255,255,255,.35);
  border-radius: 8px; margin-right: 10px; white-space: nowrap; }
#dau-phai { display: flex; align-items: center; flex-wrap: nowrap; }
#dau-phai a, #dau-phai span { white-space: nowrap; }

/* Chữ nội dung canh đều (anh Kiên 05/08) — tiêu đề và nút vẫn canh trái */
.the-hoc p, .the-hoc blockquote, .the-hoc li,
.bai-doc p, .bai-doc blockquote, .bai-doc li,
.bai-doc-long p, .bai-doc-long blockquote, .bai-doc-long li,
.ket-qua, .bang-kiem-xem { text-align: justify; }