/* ================================================
   24点训练系统 v3 - 优化排版
   特点：策略卡片网格 / 清晰层级 / 移动友好
   ================================================ */

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
    font-family: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    background: linear-gradient(135deg, #0c0c1d 0%, #1a1a3e 50%, #0d2137 100%);
    min-height: 100vh;
    padding: 12px;
    color: #e0e0e0;
}

#app { max-width: 560px; margin: 0 auto; }

/* ---- 通用 ---- */
.section-title {
    font-size: 16px;
    font-weight: bold;
    color: rgba(255,255,255,0.6);
    margin-bottom: 10px;
    padding-left: 4px;
    border-left: 3px solid #f1c40f;
    padding-left: 10px;
}

/* ---- 头部 ---- */
header { text-align: center; padding: 15px 0 8px; }
header h1 { font-size: 34px; color: #f1c40f; text-shadow: 0 2px 8px rgba(241,196,15,0.3); letter-spacing: 2px; }
.subtitle { font-size: 13px; opacity: 0.6; margin-top: 2px; }

/* ---- 策略选择（网格布局） ---- */
#strategy-section {
    margin: 12px 0;
}

#strategy-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
    gap: 8px;
}

.strat-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2px;
    padding: 12px 8px;
    border: 2px solid rgba(255,255,255,0.08);
    border-radius: 14px;
    background: rgba(255,255,255,0.04);
    color: #ccc;
    cursor: pointer;
    transition: all 0.25s;
    text-align: center;
    --strat-color: #888;
}
.strat-card:hover {
    background: rgba(255,255,255,0.08);
    transform: translateY(-3px);
    border-color: var(--strat-color);
}
.strat-card.active {
    background: linear-gradient(135deg, rgba(240,147,251,0.2), rgba(245,87,108,0.2));
    border-color: #f5576c;
    color: #fff;
    box-shadow: 0 4px 20px rgba(245,87,108,0.2);
    transform: translateY(-3px);
}

.strat-icon { font-size: 28px; }
.strat-name { font-size: 14px; font-weight: bold; }
.strat-desc { font-size: 10px; opacity: 0.6; }

/* ---- 难度选择 ---- */
#difficulty-section {
    margin: 12px 0;
}

#diff-row {
    display: flex;
    gap: 8px;
}

.diff-btn {
    flex: 1;
    padding: 10px 16px;
    border: 2px solid rgba(255,255,255,0.1);
    border-radius: 12px;
    background: rgba(255,255,255,0.04);
    color: #aaa;
    font-size: 15px;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.25s;
    text-align: center;
}
.diff-btn:hover { background: rgba(255,255,255,0.1); }
.diff-btn.active {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: #fff;
    border-color: transparent;
    box-shadow: 0 4px 15px rgba(102,126,234,0.3);
}

/* ---- 牌面 ---- */
#card-row {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin: 12px 0;
}

.card {
    width: 90px;
    height: 125px;
    background: linear-gradient(145deg, #ffffff, #f0f0f0);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 40px;
    font-weight: bold;
    color: #1a1a2e;
    box-shadow: 0 6px 20px rgba(0,0,0,0.3);
    cursor: pointer;
    transition: transform 0.15s, box-shadow 0.15s;
    user-select: none;
    border: 3px solid #ddd;
}
.card:active { transform: scale(0.9); }
.card:hover { transform: translateY(-5px); box-shadow: 0 10px 30px rgba(0,0,0,0.4); }
.card:nth-child(1) { border-color: #e74c3c; color: #e74c3c; }
.card:nth-child(2) { border-color: #2ecc71; color: #2ecc71; }
.card:nth-child(3) { border-color: #3498db; color: #3498db; }
.card:nth-child(4) { border-color: #f39c12; color: #f39c12; }
.card.pop { animation: cardPop 0.3s ease; }

@keyframes cardPop {
    0% { transform: scale(1); }
    50% { transform: scale(1.15); }
    100% { transform: scale(1); }
}

/* ---- 信息栏 ---- */
#info-bar {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 16px;
    margin: 8px 0;
    font-size: 15px;
    color: rgba(255,255,255,0.7);
    flex-wrap: wrap;
}

#timer { color: #2ecc71; font-size: 18px; font-weight: bold; }
#timer.urgent { color: #e74c3c; animation: pulse 0.5s infinite; }
#timer.warning { color: #f39c12; }

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

#diff-badge {
    padding: 2px 12px;
    border-radius: 10px;
    font-size: 12px;
    font-weight: bold;
}
.badge-hard { background: rgba(231,76,60,0.2); color: #e74c3c; }
.badge-medium { background: rgba(243,156,18,0.2); color: #f39c12; }
.badge-expert { background: rgba(155,89,182,0.2); color: #9b59b6; }

/* ---- 表达式显示 ---- */
#expr-display-area { margin: 6px 0; }

#expr-display {
    background: rgba(0,0,0,0.35);
    border: 2px solid rgba(255,255,255,0.1);
    border-radius: 12px;
    padding: 12px 16px;
    min-height: 48px;
    font-size: 24px;
    font-family: 'Courier New', monospace;
    color: #fff;
    cursor: pointer;
    text-align: center;
    letter-spacing: 2px;
    word-break: break-all;
    transition: border-color 0.3s;
}
#expr-display:focus-within { border-color: #f1c40f; }

#expr-text { color: #fff; }
#expr-text.placeholder { color: #666; font-size: 16px; }

#expr-cursor {
    animation: blink 1s step-end infinite;
    color: #f1c40f;
    font-weight: bold;
}

@keyframes blink {
    0%, 100% { opacity: 1; }
    50% { opacity: 0; }
}

#expr-preview {
    text-align: center;
    margin-top: 4px;
    font-size: 14px;
    color: #888;
    min-height: 20px;
}

/* ---- 输入面板 ---- */
#input-panel { margin: 10px 0; }

.input-row {
    display: flex;
    gap: 6px;
    justify-content: center;
    margin: 5px 0;
}

.ip-btn {
    padding: 12px 0;
    border: none;
    border-radius: 10px;
    font-size: 18px;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.15s;
    user-select: none;
    flex: 1;
    max-width: 85px;
    text-align: center;
}
.ip-btn:active { transform: scale(0.92); }

.ip-paren {
    background: rgba(255,255,255,0.08);
    color: #999;
    font-size: 22px;
}
.ip-paren:hover { background: rgba(255,255,255,0.14); }

.ip-edit {
    background: rgba(231,76,60,0.2);
    color: #e74c3c;
    font-size: 15px;
}
.ip-edit:hover { background: rgba(231,76,60,0.35); }

.ip-op {
    background: rgba(52,152,219,0.2);
    color: #5dade2;
    font-size: 17px;
}
.ip-op:hover { background: rgba(52,152,219,0.35); }

.action-row { gap: 8px; }

#btn-submit {
    flex: 2;
    padding: 14px;
    background: linear-gradient(135deg, #2ecc71, #27ae60);
    color: #fff;
    font-size: 18px;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    font-weight: bold;
    box-shadow: 0 4px 15px rgba(46,204,113,0.25);
}
#btn-submit:hover { box-shadow: 0 6px 20px rgba(46,204,113,0.4); transform: translateY(-2px); }
#btn-submit:active { transform: scale(0.95); }

#btn-hint {
    flex: 1.3;
    padding: 14px;
    background: linear-gradient(135deg, #f39c12, #e67e22);
    color: #fff;
    font-size: 16px;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    font-weight: bold;
}
#btn-hint:hover { box-shadow: 0 4px 15px rgba(243,156,18,0.3); transform: translateY(-2px); }

#btn-pass {
    flex: 1;
    padding: 14px;
    background: rgba(149,165,166,0.2);
    color: #bdc3c7;
    font-size: 15px;
    border: none;
    border-radius: 12px;
    cursor: pointer;
}
#btn-pass:hover { background: rgba(149,165,166,0.35); }

/* ---- 反馈 ---- */
#feedback {
    text-align: center;
    font-size: 18px;
    font-weight: bold;
    min-height: 44px;
    padding: 10px 14px;
    margin: 6px 0;
    border-radius: 10px;
    transition: all 0.3s;
}
#feedback.correct {
    background: rgba(46,204,113,0.12);
    color: #2ecc71;
    animation: celebrate 0.5s ease;
}
#feedback.wrong {
    background: rgba(231,76,60,0.1);
    color: #e74c3c;
    animation: shake 0.5s ease;
}
#feedback.hint {
    background: rgba(241,196,15,0.08);
    color: #f1c40f;
}

@keyframes celebrate {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.06); }
}
@keyframes shake {
    0%, 100% { transform: translateX(0); }
    20% { transform: translateX(-8px); }
    40% { transform: translateX(8px); }
    60% { transform: translateX(-5px); }
    80% { transform: translateX(5px); }
}

/* ---- 解法展示 ---- */
#solutions-section {
    background: rgba(255,255,255,0.04);
    border-radius: 14px;
    padding: 14px 16px;
    margin: 12px 0;
}
#solutions-section .section-title { margin-bottom: 8px; }

.strategy-group {
    margin: 8px 0;
    padding: 10px 12px;
    background: rgba(255,255,255,0.03);
    border-radius: 10px;
    border-left: 3px solid #555;
}
.strategy-group h3 { font-size: 14px; margin-bottom: 4px; }
.strategy-group .sol-item {
    padding: 3px 0 3px 10px;
    font-size: 15px;
    font-family: 'Courier New', monospace;
    color: #bdc3c7;
}
.strategy-group .sol-item.highlight {
    color: #f1c40f;
    background: rgba(241,196,15,0.06);
    border-radius: 4px;
    padding: 3px 8px 3px 10px;
}

/* ---- 错题本 ---- */
#wrong-section {
    background: rgba(255,255,255,0.04);
    border-radius: 14px;
    padding: 14px 16px;
    margin: 12px 0;
}
#wrong-section .section-title { color: #e74c3c; }

.wrong-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 10px;
    border-bottom: 1px solid rgba(255,255,255,0.05);
    flex-wrap: wrap;
}
.wrong-item:last-child { border-bottom: none; }
.wrong-cards { font-size: 17px; font-weight: bold; color: #fff; min-width: 75px; }
.wrong-solution { color: #2ecc71; font-size: 13px; flex: 1; font-family: monospace; }
.wrong-count { background: #e74c3c; color: #fff; border-radius: 8px; padding: 2px 8px; font-size: 11px; }
.btn-mastered {
    padding: 4px 12px;
    border: none;
    border-radius: 8px;
    background: #2ecc71;
    color: #fff;
    font-size: 12px;
    cursor: pointer;
}
.btn-mastered:hover { background: #27ae60; }

/* ---- 看板 ---- */
#stats-section {
    background: rgba(255,255,255,0.04);
    border-radius: 14px;
    padding: 14px 16px;
    margin: 12px 0;
}
#stats-section .section-title { color: #3498db; }

#stats-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
}
.stat-card {
    text-align: center;
    padding: 12px;
    background: rgba(255,255,255,0.04);
    border-radius: 10px;
}
.stat-num { font-size: 26px; font-weight: bold; color: #3498db; }
.stat-lbl { font-size: 12px; color: #888; margin-top: 2px; }

/* ---- 底部 ---- */
footer { text-align: center; padding: 20px 0 10px; }
footer p { color: rgba(255,255,255,0.3); font-size: 13px; }
.footer-small { font-size: 11px; opacity: 0.5; margin-top: 4px; }

/* ---- 响应式 ---- */
@media (max-width: 480px) {
    header h1 { font-size: 26px; }
    .card { width: 72px; height: 102px; font-size: 32px; }
    #card-row { gap: 8px; }
    #strategy-grid { grid-template-columns: repeat(auto-fill, minmax(120px, 1fr)); }
    .strat-card { padding: 10px 6px; }
    .strat-icon { font-size: 22px; }
    .ip-btn { font-size: 15px; max-width: 70px; padding: 10px 0; }
    #btn-submit { font-size: 16px; padding: 12px; }
    #expr-display { font-size: 20px; padding: 10px 12px; }
    #info-bar { font-size: 13px; gap: 10px; }
}

/* ---- 等待空格键状态 ---- */
#expr-display.waiting-next {
    border-color: #f1c40f;
    background: rgba(241, 196, 15, 0.08);
    animation: glow 1.5s ease-in-out infinite;
}

@keyframes glow {
    0%, 100% { box-shadow: 0 0 5px rgba(241, 196, 15, 0.2); }
    50% { box-shadow: 0 0 20px rgba(241, 196, 15, 0.4); }
}

#expr-text.waiting-hint {
    color: #f1c40f;
    font-size: 18px;
    letter-spacing: 3px;
}

/* 在解法区域加一个提示条 */
.next-hint-bar {
    text-align: center;
    padding: 10px;
    margin-top: 10px;
    background: rgba(241, 196, 15, 0.08);
    border-radius: 10px;
    color: #f1c40f;
    font-size: 15px;
    font-weight: bold;
    animation: pulse 1.5s ease-in-out infinite;
}