:root {
    --primary-red: #de2910;
    --primary-gold: #ffde00;
    --bg-gradient: linear-gradient(135deg, #fff1f0 0%, #ffe4e1 100%);
    --card-bg: rgba(255, 255, 255, 0.95);
    --text-dark: #2c3e50;
    --text-light: #7f8c8d;
    --border-color: #f5b7b1;
    --shadow: 0 4px 12px rgba(222, 41, 16, 0.15);
    --paper-bg: #fffbf0;

    --font-main: "Noto Serif SC", serif;
    --font-sans: "Outfit", sans-serif;
    --font-mono: "JetBrains Mono", monospace;
    --font-title: "Ma Shan Zheng", cursive;
}

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

body {
    font-family: var(--font-main);
    background: var(--bg-gradient);
    color: var(--text-dark);
    height: 100vh;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
}

.app-container {
    width: 96vw;
    height: 92vh;
    max-width: 1900px;
    background: var(--card-bg);
    border-radius: 24px;
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    border: 2px solid rgba(255, 255, 255, 0.5);
    backdrop-filter: blur(10px);
}

/* Header */
.main-header {
    padding: 1.2rem 2.5rem;
    background: linear-gradient(90deg, #de2910 0%, #b01f0c 100%);
    color: white;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

.header-content h1 {
    font-size: 1.8rem;
    margin-bottom: 4px;
    letter-spacing: 1px;
}

.highlight {
    font-family: var(--font-title);
    color: var(--primary-gold);
    font-weight: normal;
    margin-left: 10px;
}

.subtitle {
    font-family: var(--font-sans);
    font-size: 0.9rem;
    opacity: 0.9;
    font-weight: 300;
}

.header-tabs {
    display: flex;
    gap: 12px;
    background: rgba(0, 0, 0, 0.1);
    padding: 4px;
    border-radius: 12px;
}

.tab-btn {
    padding: 8px 20px;
    border: none;
    background: transparent;
    color: rgba(255, 255, 255, 0.8);
    font-family: var(--font-main);
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    border-radius: 8px;
    transition: all 0.3s ease;
}

.tab-btn:hover {
    color: white;
    background: rgba(255, 255, 255, 0.1);
}

.tab-btn.active {
    background: white;
    color: var(--primary-red);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

/* Main Stage */
.main-stage {
    flex: 1;
    display: grid;
    grid-template-columns: 1fr 320px;
    overflow: hidden;
}

.proof-workspace {
    display: grid;
    grid-template-columns: 300px 1fr;
    height: 100%;
    overflow: hidden;
}

/* Toolbox */
.toolbox-panel {
    background: #f8f9fa;
    border-right: 1px solid #eee;
    padding: 20px;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.panel-header h3 {
    color: var(--primary-red);
    font-size: 1.2rem;
    border-bottom: 2px solid var(--primary-red);
    padding-bottom: 10px;
    margin-bottom: 10px;
}

.tool-section h4 {
    font-size: 0.95rem;
    color: var(--text-light);
    margin-bottom: 10px;
    font-weight: bold;
}

.premise-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.premise-btn {
    padding: 10px;
    background: white;
    border: 1px solid #ddd;
    border-radius: 6px;
    text-align: left;
    cursor: pointer;
    font-family: var(--font-mono);
    font-size: 0.9rem;
    transition: all 0.2s;
}

.premise-btn:hover {
    border-color: var(--primary-red);
    background: #fff5f5;
}

.rule-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 8px;
}

.rule-btn {
    padding: 8px;
    background: white;
    border: 1px solid #ddd;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.85rem;
    transition: all 0.2s;
}

.rule-btn:hover {
    border-color: var(--primary-red);
    color: var(--primary-red);
}

.rule-btn.special {
    width: 100%;
    background: #e8f5e9;
    border-color: #c8e6c9;
    color: #2e7d32;
    margin-bottom: 8px;
}

.rule-btn.special:hover {
    background: #c8e6c9;
}

.hidden {
    display: none;
}

.action-row {
    margin-top: auto;
    display: flex;
    gap: 10px;
}

.control-btn {
    flex: 1;
    padding: 10px;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    background: #e0e0e0;
    color: var(--text-dark);
}

.control-btn.warning {
    background: #ffebee;
    color: var(--error-red);
}

/* Proof Panel */
.proof-panel {
    padding: 30px;
    background: #f0f2f5;
    display: flex;
    flex-direction: column;
    overflow-y: auto;
}

.goal-card {
    background: white;
    padding: 20px;
    border-radius: 12px;
    box-shadow: var(--shadow);
    margin-bottom: 20px;
    border-left: 5px solid var(--primary-gold);
}

.goal-label {
    font-size: 0.9rem;
    color: var(--text-light);
    margin-bottom: 5px;
}

.goal-formula {
    font-family: var(--font-mono);
    font-size: 1.5rem;
    color: var(--primary-red);
    margin-bottom: 8px;
}

.goal-desc {
    color: var(--text-dark);
    font-size: 1rem;
}

.proof-paper {
    background: var(--paper-bg);
    padding: 40px;
    border-radius: 4px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    min-height: 500px;
    position: relative;
    border: 1px solid #e0d0b0;
}

.paper-header {
    text-align: center;
    margin-bottom: 30px;
    border-bottom: 2px solid var(--primary-red);
    padding-bottom: 15px;
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
}

.paper-title {
    font-family: var(--font-title);
    font-size: 1.8rem;
    color: var(--primary-red);
}

.paper-id {
    font-family: var(--font-mono);
    color: var(--text-light);
    font-size: 0.9rem;
}

.proof-table {
    width: 100%;
    border-collapse: collapse;
}

.proof-table th {
    text-align: left;
    padding: 10px;
    border-bottom: 2px solid #ccc;
    color: var(--text-light);
    font-weight: normal;
    font-size: 0.9rem;
}

.proof-table td {
    padding: 12px 10px;
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
    font-family: var(--font-mono);
    font-size: 1.1rem;
}

.proof-table tr.selected {
    background: rgba(222, 41, 16, 0.05);
}

.proof-table tr:hover {
    background: rgba(0, 0, 0, 0.02);
    cursor: pointer;
}

.proof-status {
    margin-top: 30px;
    text-align: center;
    font-family: var(--font-title);
    font-size: 1.2rem;
    color: var(--text-light);
}

.proof-status.success {
    color: #27ae60;
}

/* Sidebar */
.sidebar {
    background: rgba(255, 255, 255, 0.5);
    border-left: 1px solid rgba(255, 255, 255, 0.8);
    padding: 30px;
    overflow-y: auto;
}

.panel-section {
    margin-bottom: 40px;
}

.panel-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 20px;
    padding-bottom: 10px;
    border-bottom: 2px solid var(--primary-gold);
}

.panel-icon {
    font-size: 1.5rem;
}

.panel-header h3 {
    font-size: 1.2rem;
    color: var(--primary-red);
}

.concept-content h4,
.insight-content h4 {

    .rule-btn {
        padding: 8px;
        background: white;
        border: 1px solid #ddd;
        border-radius: 6px;
        cursor: pointer;
        font-size: 0.85rem;
        transition: all 0.2s;
    }

    .rule-btn:hover {
        border-color: var(--primary-red);
        color: var(--primary-red);
    }

    .rule-btn.special {
        width: 100%;
        background: #e8f5e9;
        border-color: #c8e6c9;
        color: #2e7d32;
        margin-bottom: 8px;
    }

    .rule-btn.special:hover {
        background: #c8e6c9;
    }

    .hidden {
        display: none;
    }

    .action-row {
        margin-top: auto;
        display: flex;
        gap: 10px;
    }

    .control-btn {
        flex: 1;
        padding: 10px;
        border: none;
        border-radius: 6px;
        cursor: pointer;
        background: #e0e0e0;
        color: var(--text-dark);
    }

    .control-btn.warning {
        background: #ffebee;
        color: var(--error-red);
    }

    /* Proof Panel */
    .proof-panel {
        padding: 30px;
        background: #f0f2f5;
        display: flex;
        flex-direction: column;
        overflow-y: auto;
    }

    .goal-card {
        background: white;
        padding: 20px;
        border-radius: 12px;
        box-shadow: var(--shadow);
        margin-bottom: 20px;
        border-left: 5px solid var(--primary-gold);
    }

    .goal-label {
        font-size: 0.9rem;
        color: var(--text-light);
        margin-bottom: 5px;
    }

    .goal-formula {
        font-family: var(--font-mono);
        font-size: 1.5rem;
        color: var(--primary-red);
        margin-bottom: 8px;
    }

    .goal-desc {
        color: var(--text-dark);
        font-size: 1rem;
    }

    .proof-paper {
        background: var(--paper-bg);
        padding: 40px;
        border-radius: 4px;
        box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
        min-height: 500px;
        position: relative;
        border: 1px solid #e0d0b0;
    }

    .paper-header {
        text-align: center;
        margin-bottom: 30px;
        border-bottom: 2px solid var(--primary-red);
        padding-bottom: 15px;
        display: flex;
        justify-content: space-between;
        align-items: flex-end;
    }

    .paper-title {
        font-family: var(--font-title);
        font-size: 1.8rem;
        color: var(--primary-red);
    }

    .paper-id {
        font-family: var(--font-mono);
        color: var(--text-light);
        font-size: 0.9rem;
    }

    .proof-table {
        width: 100%;
        border-collapse: collapse;
    }

    .proof-table th {
        text-align: left;
        padding: 10px;
        border-bottom: 2px solid #ccc;
        color: var(--text-light);
        font-weight: normal;
        font-size: 0.9rem;
    }

    .proof-table td {
        padding: 12px 10px;
        border-bottom: 1px solid rgba(0, 0, 0, 0.05);
        font-family: var(--font-mono);
        font-size: 1.1rem;
    }

    .proof-table tr.selected {
        background: rgba(222, 41, 16, 0.05);
    }

    .proof-table tr:hover {
        background: rgba(0, 0, 0, 0.02);
        cursor: pointer;
    }

    .proof-status {
        margin-top: 30px;
        text-align: center;
        font-family: var(--font-title);
        font-size: 1.2rem;
        color: var(--text-light);
    }

    .proof-status.success {
        color: #27ae60;
    }

    /* Sidebar */
    .sidebar {
        background: rgba(255, 255, 255, 0.5);
        border-left: 1px solid rgba(255, 255, 255, 0.8);
        padding: 30px;
        overflow-y: auto;
    }

    .panel-section {
        margin-bottom: 40px;
    }

    .panel-header {
        display: flex;
        align-items: center;
        gap: 12px;
        margin-bottom: 20px;
        padding-bottom: 10px;
        border-bottom: 2px solid var(--primary-gold);
    }

    .panel-icon {
        font-size: 1.5rem;
    }

    .panel-header h3 {
        font-size: 1.2rem;
        color: var(--primary-red);
    }

    .concept-content h4,
    .insight-content h4 {
        color: var(--text-dark);
        margin: 16px 0 8px 0;
        font-size: 1rem;
    }

    .concept-content p,
    .insight-content p {
        color: var(--text-light);
        font-size: 0.95rem;
        line-height: 1.6;
        margin-bottom: 12px;
    }

    .rules-table {
        width: 100%;
        border-collapse: collapse;
        font-size: 0.85rem;
        margin-bottom: 15px;
    }

    .rules-table th {
        background: #f8f9fa;
        padding: 8px;
        text-align: left;
        border-bottom: 2px solid var(--primary-red);
        color: var(--text-dark);
    }

    .rules-table td {
        padding: 6px 8px;
        border-bottom: 1px solid #eee;
        font-family: var(--font-mono);
        font-size: 0.8rem;
    }

    .rules-table tr:hover {
        background: #fff5f5;
    }