* { margin: 0; padding: 0; box-sizing: border-box; }
body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
       background: #f0f2f5; color: #333; line-height: 1.6; }

.login-page { display: flex; align-items: center; justify-content: center; min-height: 100vh; padding: 20px; }
.login-box { background: #fff; padding: 30px 25px; border-radius: 12px; box-shadow: 0 2px 12px rgba(0,0,0,0.08);
             width: 100%; max-width: 380px; }
.login-box h1 { text-align: center; font-size: 22px; margin-bottom: 25px; color: #1a73e8; }

.form-item { margin-bottom: 18px; }
.form-item label { display: block; margin-bottom: 6px; font-size: 14px; color: #555; }
.form-item input, .form-item select {
    width: 100%; padding: 10px 12px; border: 1px solid #ddd; border-radius: 8px;
    font-size: 15px; outline: none;
}
.form-item input:focus, .form-item select:focus { border-color: #1a73e8; }

.btn-primary {
    width: 100%; padding: 12px; background: #1a73e8; color: #fff; border: none;
    border-radius: 8px; font-size: 16px; cursor: pointer; margin-top: 8px;
}
.btn-primary:hover { background: #1557b0; }

.error-msg { background: #fee; color: #c33; padding: 10px; border-radius: 6px; margin-bottom: 15px; font-size: 14px; text-align: center; }
.admin-link { text-align: center; margin-top: 18px; font-size: 13px; }
.admin-link a { color: #999; text-decoration: none; }

.header { background: linear-gradient(135deg, #1a73e8, #0d47a1); color: #fff; padding: 20px 15px; }
.header h1 { font-size: 20px; text-align: center; }
.user-info { text-align: center; font-size: 14px; opacity: 0.9; margin-top: 4px; }

.container { max-width: 600px; margin: 0 auto; padding: 15px; }

.semester-block { margin-bottom: 20px; }
.semester-title { font-size: 16px; color: #333; margin-bottom: 10px; padding-left: 5px; border-left: 3px solid #1a73e8; }
.project-list { display: flex; flex-direction: column; gap: 10px; }
.project-card {
    background: #fff; border-radius: 10px; padding: 15px; display: flex;
    justify-content: space-between; align-items: center; box-shadow: 0 1px 4px rgba(0,0,0,0.05);
}
.project-card.done { opacity: 0.6; }
.project-name { font-size: 15px; font-weight: 500; }
.status-done { color: #52c41a; font-size: 13px; }
.btn-start {
    background: #1a73e8; color: #fff; padding: 6px 14px; border-radius: 6px;
    font-size: 13px; text-decoration: none;
}
.empty-tip { text-align: center; color: #999; padding: 30px; font-size: 14px; }

.quiz-header { background: #fff; padding: 15px; position: sticky; top: 0; z-index: 10; box-shadow: 0 1px 3px rgba(0,0,0,0.05); }
.quiz-title { font-size: 17px; font-weight: 500; margin-bottom: 8px; text-align: center; }
.progress-bar { height: 8px; background: #e8e8e8; border-radius: 4px; overflow: hidden; margin-bottom: 5px; }
.progress-fill { height: 100%; background: #52c41a; transition: width 0.3s; }
.progress-text { text-align: right; font-size: 12px; color: #666; }

.quiz-container { padding-bottom: 80px; }
.scene-block { background: #fff; border-radius: 10px; padding: 15px; margin-bottom: 15px; }
.scene-desc { background: #f0f7ff; padding: 12px; border-radius: 8px; margin-bottom: 15px; font-size: 18px; color: #1a73e8; }

.question-block { margin-bottom: 20px; padding-bottom: 15px; border-bottom: 1px dashed #eee; }
.question-block:last-child { border-bottom: none; margin-bottom: 0; }
.question-title { font-size: 18px; margin-bottom: 12px; font-weight: 500; }

.options-list { display: flex; flex-direction: column; gap: 8px; }
.option-item {
    display: flex; align-items: flex-start; padding: 10px 12px; border: 1px solid #ddd;
    border-radius: 8px; cursor: pointer; transition: all 0.2s;
}
.option-item input { margin-right: 10px; margin-top: 3px; }
.option-text { flex: 1; font-size: 17px; }

.option-item.correct { background: #f6ffed; border-color: #52c41a; color: #389e0d; }
.option-item.wrong { background: #fff1f0; border-color: #ff4d4f; color: #cf1322; }

.tip-box {
    margin-top: 10px; padding: 10px; background: #fffbe6; border-left: 3px solid #faad14;
    border-radius: 4px; font-size: 16px; color: #d46b08;
}

.btn-submit { position: fixed; bottom: 0; left: 0; right: 0; max-width: 600px; margin: 0 auto;
              border-radius: 0; padding: 14px; font-size: 16px; }

.modal { position: fixed; top: 0; left: 0; right: 0; bottom: 0; background: rgba(0,0,0,0.5);
         display: flex; align-items: center; justify-content: center; z-index: 100; padding: 20px; }
.modal-content { background: #fff; padding: 30px 25px; border-radius: 12px; width: 100%; max-width: 320px; text-align: center; }
.modal-content h3 { margin-bottom: 15px; }
.modal-content p { margin-bottom: 10px; font-size: 15px; }
.modal-content .btn-primary { margin-top: 15px; display: inline-block; text-decoration: none; }

@media (max-width: 480px) {
    .login-box { padding: 25px 20px; }
    .header h1 { font-size: 18px; }
}