/* ===== course.css - Shared Course Stylesheet (暗色科技风) ===== */
*{margin:0;padding:0;box-sizing:border-box}
body{font-family:"Microsoft YaHei","PingFang SC","Helvetica Neue",Arial,sans-serif;background:#0a0e1a;color:#e2e8f0}
.lesson-body{min-height:100vh;background:#0a0e1a}

/* ===== Navbar ===== */
.lesson-navbar{display:flex;justify-content:space-between;align-items:center;padding:10px 24px;background:rgba(15,21,36,0.95);box-shadow:0 2px 12px rgba(0,0,0,0.3);position:sticky;top:0;z-index:100;backdrop-filter:blur(12px)}
.nav-left{display:flex;align-items:center;gap:16px}
.back-btn{text-decoration:none;color:#60a5fa;font-size:14px;font-weight:600;padding:6px 14px;border:1px solid rgba(59,130,246,0.3);border-radius:8px;transition:all .2s}
.back-btn:hover{background:rgba(59,130,246,0.1)}
.lesson-breadcrumb{font-size:13px;color:#64748b}
.nav-right{display:flex;align-items:center}
.stage-progress{display:flex;gap:4px}
.sp-dot{width:10px;height:10px;border-radius:50%;background:#334155;transition:all .3s;cursor:pointer}
.sp-dot.active{background:#3b82f6;transform:scale(1.3)}
.sp-dot.done{background:#22c55e}

/* ===== Lesson Container ===== */
.lesson-container{max-width:900px;margin:20px auto;padding:0 16px 80px}
.stage-content{display:none;animation:fadeIn .4s ease}
.stage-content.active{display:block}
@keyframes fadeIn{from{opacity:0;transform:translateY(10px)}to{opacity:1;transform:translateY(0)}}

/* ===== Cover Stage ===== */
.lesson-cover{text-align:center;padding:50px 30px;background:#141b2d;border:1px solid #1e293b;border-radius:12px;box-shadow:0 4px 16px rgba(0,0,0,0.3)}
.cover-tag{display:inline-block;padding:6px 18px;background:rgba(59,130,246,0.15);color:#60a5fa;border:1px solid rgba(59,130,246,0.3);border-radius:6px;font-size:14px;font-weight:600;margin-bottom:20px}
.cover-title{font-size:42px;font-weight:800;color:#e2e8f0;margin-bottom:12px}
.cover-subtitle{font-size:18px;color:#64748b;margin-bottom:30px}
.cover-start-btn{padding:14px 40px;font-size:17px;font-weight:700;color:#fff;background:#3b82f6;border:none;border-radius:8px;cursor:pointer;box-shadow:0 4px 16px rgba(59,130,246,0.2);transition:all .3s}
.cover-start-btn:hover{transform:translateY(-2px);box-shadow:0 6px 24px rgba(59,130,246,0.3)}

/* ===== Knowledge Stage ===== */
.kp-section{background:#141b2d;border:1px solid #1e293b;border-radius:10px;padding:30px;box-shadow:0 4px 16px rgba(0,0,0,0.2)}
.kp-section h2{font-size:24px;color:#e2e8f0;margin-bottom:20px;border-bottom:1px solid #1e293b;padding-bottom:10px}
.objective-card{background:rgba(34,197,94,0.08);border-left:3px solid #22c55e;border-radius:8px;padding:16px 20px;margin-bottom:24px}
.objective-card h3{font-size:16px;color:#4ade80;margin-bottom:10px}
.objective-list{list-style:none;padding-left:0}
.objective-list li{padding:5px 0 5px 24px;position:relative;color:#94a3b8;font-size:14px;line-height:1.8}
.objective-list li::before{content:'✓';position:absolute;left:0;color:#22c55e;font-weight:bold}
.kp-sub-title{font-size:18px;font-weight:700;color:#60a5fa;margin:24px 0 12px;padding-left:12px;border-left:3px solid #3b82f6}
.def-box{background:rgba(59,130,246,0.06);border:1px solid rgba(59,130,246,0.15);border-radius:8px;padding:16px 20px;margin-bottom:16px}
.def-label{font-size:14px;font-weight:700;color:#60a5fa;margin-bottom:8px}
.def-text{font-size:15px;color:#94a3b8;line-height:1.9}
.def-text strong{color:#e2e8f0}
.tip-box{background:rgba(245,158,11,0.08);border:1px solid rgba(245,158,11,0.15);border-radius:8px;padding:16px 20px;margin-bottom:16px}
.tip-label{font-size:14px;font-weight:700;color:#f59e0b;margin-bottom:8px}
.tip-text{font-size:14px;color:#94a3b8;line-height:1.9}
.tip-text ul{padding-left:18px}
.tip-text li{padding:3px 0}
.physics-quantity{display:flex;gap:12px;flex-wrap:wrap;margin-bottom:16px}
.pq-card{flex:1;min-width:140px;background:rgba(168,85,247,0.08);border:1px solid rgba(168,85,247,0.15);border-radius:8px;padding:14px;text-align:center}
.pq-name{font-size:13px;color:#c084fc;font-weight:600;margin-bottom:4px}
.pq-symbol{font-size:28px;color:#d8b4fe;font-weight:800;font-style:italic}
.pq-formula{font-size:13px;color:#c084fc;margin-top:4px}
.pq-unit{font-size:12px;color:#a78bfa}

/* ===== Animation Stage ===== */
.animation-stage{background:#141b2d;border:1px solid #1e293b;border-radius:10px;padding:24px;box-shadow:0 4px 16px rgba(0,0,0,0.2)}
.animation-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:16px;flex-wrap:wrap;gap:10px}
.animation-header h2{font-size:22px;color:#e2e8f0}
.anim-controls{display:flex;gap:10px}
.anim-btn{padding:8px 20px;font-size:14px;font-weight:600;border:none;border-radius:8px;cursor:pointer;transition:all .2s}
.anim-btn-play{background:#22c55e;color:#fff}
.anim-btn-play.playing{background:#f59e0b}
.anim-btn-reset{background:#475569;color:#fff}
.anim-btn:hover{transform:translateY(-1px);box-shadow:0 3px 10px rgba(0,0,0,0.3)}
/* Canvas区域保持白色背景，确保动画可读性 */
.anim-canvas-wrap{background:#fff;border:1px solid #1e293b;border-radius:8px;padding:10px;display:flex;justify-content:center;margin-bottom:16px;overflow:auto}
.anim-canvas-wrap canvas{max-width:100%;height:auto;border-radius:4px}
.anim-narration{display:flex;align-items:flex-start;gap:12px;background:rgba(59,130,246,0.08);border-radius:8px;padding:14px 18px;min-height:60px}
.narr-icon{font-size:20px;flex-shrink:0}
.narr-text{font-size:15px;color:#94a3b8;line-height:1.7}
.anim-step-bar{display:flex;gap:6px;justify-content:center;margin-top:14px;flex-wrap:wrap}
.asb-dot{width:28px;height:28px;border-radius:50%;background:#1e293b;color:#64748b;display:flex;align-items:center;justify-content:center;font-size:12px;font-weight:600;cursor:pointer;transition:all .3s}
.asb-dot.active{background:#3b82f6;color:#fff;transform:scale(1.15)}
.asb-dot.done{background:#22c55e;color:#fff}

/* ===== Experiment Stage ===== */
.experiment-stage{background:#141b2d;border:1px solid #1e293b;border-radius:10px;padding:24px;box-shadow:0 4px 16px rgba(0,0,0,0.2)}
.experiment-stage h2{font-size:22px;color:#e2e8f0;margin-bottom:12px}
.hint-bar{background:rgba(245,158,11,0.08);border-left:3px solid #f59e0b;border-radius:8px;padding:10px 16px;font-size:14px;color:#f59e0b;margin-bottom:16px}
.exp-layout{display:flex;gap:20px;flex-wrap:wrap}
.exp-canvas-area{flex:1;min-width:320px}
/* Canvas区域保持白色背景 */
.exp-canvas-wrap{background:#fff;border:1px solid #1e293b;border-radius:8px;padding:10px;display:flex;justify-content:center}
.exp-canvas-wrap canvas{max-width:100%;height:auto;border-radius:4px}
.exp-controls-area{width:280px}
.exp-control-group{background:#0f1524;border:1px solid #1e293b;border-radius:8px;padding:16px;margin-bottom:16px}
.ecg-title{font-size:15px;font-weight:700;color:#e2e8f0;margin-bottom:12px}
.exp-slider-row{margin-bottom:14px}
.exp-slider-row label{display:flex;justify-content:space-between;font-size:13px;color:#64748b;margin-bottom:6px}
.slider-value{font-weight:700;color:#3b82f6}
.exp-slider{width:100%;height:6px;border-radius:3px;background:#1e293b;outline:none;-webkit-appearance:none;appearance:none}
.exp-slider::-webkit-slider-thumb{-webkit-appearance:none;width:18px;height:18px;border-radius:50%;background:#3b82f6;cursor:pointer;border:2px solid #0a0e1a;box-shadow:0 2px 6px rgba(0,0,0,0.3)}
.exp-slider::-moz-range-thumb{width:18px;height:18px;border-radius:50%;background:#3b82f6;cursor:pointer;border:2px solid #0a0e1a}
.exp-data-display{background:rgba(34,197,94,0.08);border:1px solid rgba(34,197,94,0.15);border-radius:8px;padding:14px;margin-bottom:16px}
.exp-data-row{display:flex;justify-content:space-between;padding:5px 0;border-bottom:1px solid rgba(34,197,94,0.1)}
.exp-data-row:last-child{border-bottom:none}
.edr-label{font-size:13px;color:#4ade80}
.edr-value{font-size:14px;font-weight:700;color:#22c55e}
.exp-btn{padding:10px 20px;font-size:14px;font-weight:600;border:none;border-radius:8px;cursor:pointer;width:100%;transition:all .2s}
.exp-btn-reset{background:#475569;color:#fff}
.exp-btn-reset:hover{transform:translateY(-1px);box-shadow:0 3px 10px rgba(0,0,0,0.3)}
.exp-conclusion{background:rgba(59,130,246,0.08);border:1px solid rgba(59,130,246,0.15);border-radius:8px;padding:16px 20px;margin-top:16px}
.ec-label{font-size:14px;font-weight:700;color:#60a5fa;margin-bottom:8px}
.ec-text{font-size:14px;color:#94a3b8;line-height:1.8}

/* ===== Example Stage ===== */
.example-section{background:#141b2d;border:1px solid #1e293b;border-radius:10px;padding:24px;box-shadow:0 4px 16px rgba(0,0,0,0.2)}
.example-section h2{font-size:22px;color:#e2e8f0;margin-bottom:12px}
.ex-item{background:#0f1524;border:1px solid #1e293b;border-radius:8px;padding:20px;margin-bottom:20px}
.ex-header{display:flex;align-items:center;gap:12px;margin-bottom:14px}
.ex-badge{background:rgba(239,68,68,0.15);color:#f87171;border:1px solid rgba(239,68,68,0.3);padding:4px 14px;border-radius:6px;font-size:13px;font-weight:700}
.ex-title{font-size:17px;font-weight:600;color:#e2e8f0}
.ex-question{font-size:15px;color:#94a3b8;line-height:1.9;padding:14px;background:rgba(245,158,11,0.06);border-radius:8px;margin-bottom:14px}
.ex-solution{position:relative}
.sol-title{font-size:14px;font-weight:700;color:#60a5fa;margin-bottom:12px}
.sol-step{display:none;padding:8px 0 8px 36px;position:relative;font-size:14px;color:#94a3b8;line-height:1.8}
.sol-step.show{display:block;animation:fadeIn .3s ease}
.step-num{position:absolute;left:0;top:8px;width:24px;height:24px;background:#3b82f6;color:#fff;border-radius:50%;display:flex;align-items:center;justify-content:center;font-size:12px;font-weight:700}
.step-label{font-weight:700;color:#60a5fa}
.sol-answer{display:none;margin-top:14px;padding:14px;background:rgba(34,197,94,0.08);border-radius:8px;font-size:14px;color:#4ade80;line-height:1.8}
.sol-answer.show{display:block;animation:fadeIn .3s ease}
.ex-controls{margin-top:14px}
.ex-next-btn{padding:8px 24px;background:#3b82f6;color:#fff;border:none;border-radius:8px;font-size:14px;font-weight:600;cursor:pointer;transition:all .2s}
.ex-next-btn:hover{transform:translateY(-1px);box-shadow:0 3px 10px rgba(59,130,246,0.3)}
.ex-next-btn:disabled{background:#1e293b;color:#475569;cursor:not-allowed;transform:none;box-shadow:none}

/* ===== Extend Stage ===== */
.extend-section{background:#141b2d;border:1px solid #1e293b;border-radius:10px;padding:24px;box-shadow:0 4px 16px rgba(0,0,0,0.2)}
.extend-section h2{font-size:22px;color:#e2e8f0;margin-bottom:16px}
.extend-card{background:rgba(168,85,247,0.08);border:1px solid rgba(168,85,247,0.15);border-radius:8px;padding:18px 22px;margin-bottom:16px}
.extend-card h3{font-size:17px;color:#c084fc;margin-bottom:10px}
.extend-card p{font-size:14px;color:#94a3b8;line-height:1.8;margin-bottom:8px}

/* ===== Practice Stage ===== */
.practice-section{background:#141b2d;border:1px solid #1e293b;border-radius:10px;padding:24px;box-shadow:0 4px 16px rgba(0,0,0,0.2)}
.practice-section h2{font-size:22px;color:#e2e8f0;margin-bottom:12px}
.practice-item{background:#0f1524;border:1px solid #1e293b;border-radius:8px;padding:18px 20px;margin-bottom:16px}
.pr-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px}
.pr-num{font-size:15px;font-weight:700;color:#60a5fa}
.pr-difficulty{font-size:12px;color:#fff;padding:3px 10px;border-radius:4px;background:#475569}
.pr-question{font-size:15px;color:#94a3b8;line-height:1.8;margin-bottom:14px}
.pr-options{display:flex;flex-direction:column;gap:8px}
.pr-option{display:flex;align-items:center;gap:10px;padding:10px 14px;background:#0a0e1a;border:1px solid #1e293b;border-radius:8px;cursor:pointer;transition:all .2s;font-size:14px;color:#94a3b8}
.pr-option:hover{border-color:rgba(59,130,246,0.3);background:#0f1524}
.pr-option.selected{border-color:#3b82f6;background:rgba(59,130,246,0.1)}
.pr-option.correct{border-color:#22c55e;background:rgba(34,197,94,0.1)}
.pr-option.wrong{border-color:#ef4444;background:rgba(239,68,68,0.1)}
.pr-option.disabled{cursor:not-allowed;opacity:0.6}
.opt-letter{display:flex;align-items:center;justify-content:center;width:26px;height:26px;background:#1e293b;color:#64748b;border-radius:50%;font-weight:700;font-size:13px;flex-shrink:0;transition:all .2s}
.pr-option.selected .opt-letter{background:#3b82f6;color:#fff}
.pr-option.correct .opt-letter{background:#22c55e;color:#fff}
.pr-option.wrong .opt-letter{background:#ef4444;color:#fff}
.pr-feedback{display:none;margin-top:12px;padding:12px 16px;border-radius:8px;font-size:14px;line-height:1.7}
.pr-feedback.show{display:block;animation:fadeIn .3s ease}
.pr-feedback.correct{background:rgba(34,197,94,0.1);color:#4ade80}
.pr-feedback.wrong{background:rgba(239,68,68,0.1);color:#f87171}
.pr-input-row{display:flex;gap:10px;margin-top:8px}
.pr-input{flex:1;padding:10px 14px;background:#0a0e1a;border:1px solid #1e293b;color:#e2e8f0;border-radius:8px;font-size:14px;outline:none;transition:border .2s}
.pr-input:focus{border-color:#3b82f6}
.pr-input::placeholder{color:#475569}
.pr-submit-btn{padding:10px 20px;background:#3b82f6;color:#fff;border:none;border-radius:8px;font-size:14px;font-weight:600;cursor:pointer;transition:all .2s}
.pr-submit-btn:hover{transform:translateY(-1px);box-shadow:0 3px 10px rgba(59,130,246,0.3)}
.pr-summary{margin-top:20px;padding:16px;border-radius:8px;text-align:center;font-size:16px;font-weight:700;display:none}
.pr-summary.show{display:block;animation:fadeIn .3s ease}

/* ===== Quiz Stage ===== */
.quiz-section{background:#141b2d;border:1px solid #1e293b;border-radius:10px;padding:24px;box-shadow:0 4px 16px rgba(0,0,0,0.2)}
.quiz-section h2{font-size:22px;color:#e2e8f0;margin-bottom:12px}
.quiz-intro{font-size:14px;color:#64748b;line-height:1.8;margin-bottom:20px;padding:12px 16px;background:rgba(59,130,246,0.06);border-radius:8px}
.quiz-card{background:#0f1524;border:1px solid #1e293b;border-radius:8px;padding:20px;margin-bottom:16px}
.quiz-q-label{font-size:14px;font-weight:700;color:#60a5fa;margin-bottom:10px}
.quiz-question{font-size:16px;color:#94a3b8;line-height:1.8;margin-bottom:16px}
.quiz-answer-area{display:none}
.quiz-answer-area.show{display:block;animation:fadeIn .3s ease}
.quiz-answer{padding:14px;background:rgba(34,197,94,0.08);border-radius:8px;font-size:14px;color:#4ade80;line-height:1.8}
.quiz-show-btn{padding:8px 20px;background:#8b5cf6;color:#fff;border:none;border-radius:8px;font-size:14px;font-weight:600;cursor:pointer;transition:all .2s}
.quiz-show-btn:hover{transform:translateY(-1px);box-shadow:0 3px 10px rgba(139,92,246,0.3)}
.quiz-restart-btn{padding:10px 28px;background:#0d9488;color:#fff;border:none;border-radius:8px;font-size:15px;font-weight:600;cursor:pointer;margin-top:16px;transition:all .2s}
.quiz-restart-btn:hover{transform:translateY(-1px);box-shadow:0 4px 14px rgba(13,148,136,0.3)}

/* ===== Complete Stage ===== */
.lesson-complete{text-align:center;padding:50px 30px;background:#141b2d;border:1px solid #1e293b;border-radius:12px;box-shadow:0 4px 16px rgba(0,0,0,0.3)}
.complete-icon{font-size:64px;margin-bottom:16px}
.lesson-complete h2{font-size:28px;color:#e2e8f0;margin-bottom:12px}
.lesson-complete p{font-size:16px;color:#64748b;line-height:1.8}

/* ===== Stage Navigation ===== */
.stage-nav{position:fixed;bottom:0;left:0;right:0;display:flex;justify-content:space-between;padding:12px 24px;background:rgba(15,21,36,0.95);box-shadow:0 -2px 12px rgba(0,0,0,0.3);z-index:100;max-width:900px;margin:0 auto;backdrop-filter:blur(12px)}
.stage-nav-btn{padding:10px 24px;font-size:15px;font-weight:600;border:none;border-radius:8px;cursor:pointer;transition:all .2s;text-decoration:none;display:inline-block}
.stage-nav-btn.prev{background:#475569;color:#fff}
.stage-nav-btn.next{background:#3b82f6;color:#fff}
.stage-nav-btn:hover{transform:translateY(-2px);box-shadow:0 4px 14px rgba(0,0,0,0.3)}
.stage-nav-btn:disabled{background:#1e293b;color:#475569;cursor:not-allowed;transform:none;box-shadow:none}
.enter-next-btn{display:block;margin:24px auto 0;padding:12px 32px;font-size:15px;font-weight:600;color:#fff;background:#3b82f6;border:none;border-radius:8px;cursor:pointer;transition:all .3s}
.enter-next-btn:hover{transform:translateY(-2px);box-shadow:0 6px 20px rgba(59,130,246,0.3)}

/* ===== Index Page ===== */
.index-hero{text-align:center;padding:60px 20px 40px;background:#0f1524;border:1px solid #1e293b;color:#e2e8f0;border-radius:0 0 12px 12px}
.index-hero h1{font-size:36px;margin-bottom:10px}
.index-hero p{font-size:16px;color:#64748b}
.index-chapter{max-width:800px;margin:30px auto;padding:0 16px}
.chapter-card{background:#141b2d;border:1px solid #1e293b;border-radius:10px;padding:24px;margin-bottom:24px;box-shadow:0 4px 16px rgba(0,0,0,0.2)}
.chapter-card h2{font-size:22px;color:#e2e8f0;margin-bottom:16px;padding-bottom:10px;border-bottom:1px solid #1e293b}
.lesson-link{display:flex;align-items:center;gap:12px;padding:14px 18px;background:#0f1524;border-radius:8px;margin-bottom:10px;text-decoration:none;color:#94a3b8;transition:all .2s;border-left:3px solid transparent}
.lesson-link:hover{background:rgba(59,130,246,0.1);border-left-color:#3b82f6;transform:translateX(4px)}
.lesson-link-num{font-size:18px;font-weight:800;color:#3b82f6;min-width:40px}
.lesson-link-title{font-size:16px;font-weight:600}
.lesson-link-arrow{margin-left:auto;color:#475569}

/* ===== Responsive ===== */
@media(max-width:700px){
  .lesson-container{padding:0 8px 80px}
  .cover-title{font-size:28px}
  .exp-layout{flex-direction:column}
  .exp-controls-area{width:100%}
  .stage-nav-btn{padding:8px 16px;font-size:13px}
}