* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: -apple-system, "PingFang SC", "Microsoft YaHei", sans-serif;
  background: #f4f6fb;
  color: #22303f;
}

.login-body {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
}
.login-card {
  background: white;
  padding: 2rem 2.5rem;
  border-radius: 16px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.08);
  width: min(90vw, 320px);
  text-align: center;
}
.login-card h1 { margin-bottom: 0.25rem; font-size: 1.4rem; }
.subtitle { color: #7a8899; margin-top: 0; }
.login-card input {
  width: 100%;
  padding: 0.75rem;
  margin: 1rem 0;
  border-radius: 8px;
  border: 1px solid #d9dfe8;
  font-size: 1rem;
}
.login-card button {
  width: 100%;
  padding: 0.75rem;
  border: none;
  border-radius: 8px;
  background: #4a7dff;
  color: white;
  font-size: 1rem;
  cursor: pointer;
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.25rem 1.5rem;
  background: linear-gradient(135deg, #4a7dff, #6fa1ff);
  color: white;
}
.topbar h1 { margin: 0; font-size: 1.3rem; }
.goal { margin: 0.2rem 0 0; opacity: 0.9; font-size: 0.9rem; }
.logout { color: white; text-decoration: none; font-size: 0.9rem; opacity: 0.85; }

#app {
  max-width: 560px;
  margin: 1.25rem auto;
  padding: 0 1rem;
}

.card {
  background: white;
  border-radius: 14px;
  padding: 1.25rem;
  margin-bottom: 1rem;
  box-shadow: 0 4px 16px rgba(0,0,0,0.05);
}

.timer {
  margin-top: 0.5rem;
  font-weight: 600;
  color: #4a7dff;
}

.hint { color: #7a8899; font-size: 0.9rem; margin-top: -0.5rem; }
.field-hint { color: #7a8899; font-size: 0.85rem; margin-top: 0.4rem; }

.subject-input { margin-bottom: 0.9rem; }
.subject-input label { display: block; font-weight: 600; margin-bottom: 0.3rem; }
.subject-input textarea {
  width: 100%;
  min-height: 60px;
  padding: 0.6rem;
  border-radius: 8px;
  border: 1px solid #d9dfe8;
  font-size: 0.95rem;
  font-family: inherit;
}

#start-btn, #submit-answer-btn, #next-question-btn {
  width: 100%;
  padding: 0.8rem;
  border: none;
  border-radius: 10px;
  background: #4a7dff;
  color: white;
  font-size: 1rem;
  cursor: pointer;
  margin-top: 0.5rem;
}
#start-btn:disabled { opacity: 0.6; }

.error { color: #e0483f; font-size: 0.9rem; }

.quiz-progress {
  display: flex;
  justify-content: space-between;
  color: #7a8899;
  font-size: 0.85rem;
  margin-bottom: 0.4rem;
}
.knowledge-tag {
  display: inline-block;
  background: #eef2ff;
  color: #4a5fff;
  padding: 0.15rem 0.6rem;
  border-radius: 999px;
  font-size: 0.8rem;
  margin-bottom: 0.6rem;
}
.knowledge-tag.challenge {
  background: #fff0e0;
  color: #c76b00;
}

.stop-btn {
  width: 100%;
  padding: 0.6rem;
  border: 1px solid #d9dfe8;
  border-radius: 10px;
  background: transparent;
  color: #7a8899;
  font-size: 0.85rem;
  cursor: pointer;
  margin-top: 0.8rem;
}
#quiz-question { font-size: 1.1rem; line-height: 1.5; margin-bottom: 1rem; }

.option {
  display: block;
  padding: 0.6rem;
  border: 1px solid #d9dfe8;
  border-radius: 8px;
  margin-bottom: 0.5rem;
  cursor: pointer;
}
#quiz-fill-input, #quiz-open-input {
  width: 100%;
  padding: 0.6rem;
  border-radius: 8px;
  border: 1px solid #d9dfe8;
  font-family: inherit;
  font-size: 0.95rem;
}
#quiz-open-input { min-height: 90px; }

.feedback {
  margin-top: 0.9rem;
  padding: 0.75rem;
  border-radius: 8px;
  font-size: 0.95rem;
  line-height: 1.5;
}
.feedback.correct { background: #e8f8ee; color: #1c8a4b; }
.feedback.wrong { background: #fdecea; color: #c0392b; }

.encouragement {
  margin-top: 0.8rem;
  padding: 0.75rem;
  background: #fff8e6;
  border-radius: 8px;
  color: #8a6d1c;
}

#weak-points-list { padding-left: 1.2rem; color: #445; }
#weak-points-list li { margin-bottom: 0.3rem; }