:root {
    --primary-color: #00ffff;
    --accent-color: #ff00ff;
    --glass-bg: rgba(10, 15, 30, 0.65);
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-blur: blur(12px);
    --text-color: #ffffff;
    --text-dim: #a0a0a0;
    --panel-width: 320px;
    --radius-md: 16px;
    --radius-sm: 8px;
    --shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
}

body {
    margin: 0;
    overflow: hidden;
    background-color: #030305;
    /* Deep space black */
    font-family: 'Outfit', sans-serif;
    color: var(--text-color);
    user-select: none;
    touch-action: none;
}

/* UI Layer */
#ui-layer {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    display: flex;
    justify-content: space-between;
    padding: 0;
    box-sizing: border-box;
    z-index: 100;
}

/* SIDEBAR MENU (Left) */
#sidebar {
    width: var(--panel-width);
    height: 100%;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    -webkit-backdrop-filter: var(--glass-blur);
    border-right: 1px solid var(--glass-border);
    padding: 24px;
    pointer-events: auto;
    display: flex;
    flex-direction: column;
    box-shadow: var(--shadow);
    z-index: 200;
    overflow-y: auto;
    position: absolute;
    left: 0;
    top: 0;
    transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

#sidebar.hidden {
    transform: translateX(-100%);
}

/* Sidebar Toggle Button */
#sidebar-toggle {
    position: absolute;
    top: 24px;
    left: 24px;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border: 1px solid var(--glass-border);
    color: var(--primary-color);
    width: 48px;
    height: 48px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    z-index: 201;
    pointer-events: auto;
    font-size: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s cubic-bezier(0.16, 1, 0.3, 1);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

#sidebar-toggle:hover {
    border-color: var(--primary-color);
    box-shadow: 0 0 15px rgba(0, 255, 255, 0.3);
    transform: scale(1.05);
}

#sidebar-toggle.active {
    left: 280px;
    /* Aligned with sidebar content */
    background: transparent;
    border: none;
    box-shadow: none;
}

#header {
    margin-bottom: 24px;
    border-bottom: 1px solid var(--glass-border);
    padding-bottom: 20px;
    padding-top: 50px;
}

/* Language Switcher */
.lang-switch {
    display: flex;
    gap: 8px;
    margin-bottom: 20px;
}

.lang-btn {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid transparent;
    color: var(--text-dim);
    padding: 8px 12px;
    cursor: pointer;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 600;
    font-family: 'Outfit', sans-serif;
    flex-grow: 1;
    transition: all 0.2s;
}

.lang-btn.active {
    background: rgba(0, 255, 255, 0.15);
    border-color: var(--primary-color);
    color: #fff;
}

.lang-btn:hover:not(.active) {
    background: rgba(255, 255, 255, 0.1);
    color: #fff;
}

h1 {
    color: var(--text-color);
    margin: 0;
    font-size: 26px;
    font-weight: 800;
    background: linear-gradient(90deg, #fff, #b3fcfc);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -0.5px;
    line-height: 1.2;
}

.subtitle {
    color: var(--text-dim);
    font-size: 14px;
    margin-top: 6px;
    font-weight: 400;
}

.menu-label {
    color: var(--accent-color);
    font-size: 12px;
    font-weight: 800;
    text-transform: uppercase;
    margin-top: 24px;
    margin-bottom: 12px;
    letter-spacing: 1.5px;
    opacity: 0.9;
}

.menu-btn {
    background: transparent;
    border: 1px solid transparent;
    color: var(--text-dim);
    padding: 12px 14px;
    margin-bottom: 4px;
    text-align: left;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    font-size: 15px;
    font-family: 'Outfit', sans-serif;
    font-weight: 500;
}

.menu-btn:hover {
    background: rgba(255, 255, 255, 0.05);
    color: #fff;
    transform: translateX(4px);
}

.menu-btn.active {
    background: linear-gradient(90deg, rgba(0, 255, 255, 0.1), transparent);
    border-left: 3px solid var(--primary-color);
    color: #fff;
    /* border-radius: 0 var(--radius-sm) var(--radius-sm) 0; */
}

.menu-btn .icon {
    margin-right: 12px;
    width: 8px;
    height: 8px;
    border-radius: 50%;
    display: inline-block;
    box-shadow: 0 0 8px currentColor;
}

/* SCROLLBAR */
::-webkit-scrollbar {
    width: 6px;
}

::-webkit-scrollbar-track {
    background: rgba(0, 0, 0, 0.1);
}

::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.1);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: rgba(255, 255, 255, 0.2);
}

/* GAMES SECTION */
#games-section {
    display: block;
    margin-top: 24px;
    border-top: 1px solid var(--glass-border);
    padding-top: 24px;
    animation: fadeIn 0.6s ease;
}

.game-btn {
    background: linear-gradient(90deg, rgba(255, 0, 255, 0.1), transparent);
    border: 1px solid rgba(255, 0, 255, 0.3);
    color: var(--accent-color);
    font-weight: 600;
}

.game-btn:hover {
    background: rgba(255, 0, 255, 0.15);
    border-color: var(--accent-color);
    color: #fff;
    box-shadow: 0 0 15px rgba(255, 0, 255, 0.2);
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* INFO PANEL */
#info-panel {
    width: 360px;
    height: 100%;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    -webkit-backdrop-filter: var(--glass-blur);
    border-left: 1px solid var(--glass-border);
    padding: 0;
    pointer-events: auto;
    position: absolute;
    right: 0;
    top: 0;
    transform: translateX(100%);
    transition: transform 0.5s cubic-bezier(0.19, 1, 0.22, 1), height 0.3s ease;
    display: flex;
    flex-direction: column;
    box-shadow: -10px 0 40px rgba(0, 0, 0, 0.5);
    z-index: 200;
}

#info-panel.active {
    transform: translateX(0);
}

#info-panel.minimized {
    height: auto;
    max-height: 72px;
    background: rgba(10, 15, 30, 0.85);
    border-bottom: 1px solid var(--primary-color);
}

#info-panel.minimized .panel-content {
    display: none;
}

.panel-header {
    padding: 24px;
    font-size: 22px;
    font-weight: 800;
    color: #fff;
    border-bottom: 1px solid var(--glass-border);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: rgba(0, 0, 0, 0.2);
}

.panel-controls {
    display: flex;
    gap: 10px;
    align-items: center;
}

.panel-content {
    padding: 24px;
    overflow-y: auto;
    flex-grow: 1;
}

.formula-box {
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    padding: 20px;
    margin-bottom: 24px;
    text-align: center;
    box-shadow: inset 0 0 20px rgba(0, 0, 0, 0.2);
}

.formula-row {
    margin: 12px 0;
}

.formula-label {
    display: block;
    color: var(--text-dim);
    font-size: 11px;
    margin-bottom: 4px;
    text-transform: uppercase;
    letter-spacing: 1px;
    font-weight: 600;
}

.formula-math {
    color: #ffe600;
    font-family: 'Times New Roman', serif;
    font-size: 28px;
    text-shadow: 0 0 15px rgba(255, 230, 0, 0.15);
    font-style: italic;
}

.explanation {
    font-size: 16px;
    line-height: 1.6;
    color: #e0e0e0;
    margin-bottom: 24px;
    font-weight: 300;
}

.property-list {
    list-style: none;
    padding: 0;
    color: #ccc;
    margin-bottom: 24px;
    font-size: 15px;
}

.property-list li {
    margin-bottom: 10px;
    padding-left: 24px;
    position: relative;
}

.property-list li::before {
    content: "•";
    color: var(--accent-color);
    font-size: 20px;
    position: absolute;
    left: 0;
    top: -5px;
}

.concept-box {
    background: linear-gradient(180deg, rgba(0, 255, 100, 0.05), rgba(0, 0, 0, 0));
    border-top: 2px solid #00ff66;
    padding: 20px;
    margin-top: 10px;
    border-radius: var(--radius-sm);
}

.concept-title {
    color: #00ff66;
    font-weight: 700;
    display: block;
    margin-bottom: 10px;
    text-transform: uppercase;
    font-size: 0.85em;
    letter-spacing: 1.2px;
}

.concept-text {
    color: #e0ffe0;
    font-size: 15px;
    font-style: italic;
    line-height: 1.5;
    font-weight: 300;
}

.dim-legend {
    margin-top: 16px;
    font-size: 12px;
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}

.dim-item {
    display: flex;
    align-items: center;
    color: var(--text-dim);
    font-weight: 500;
}

.dim-item span {
    display: inline-block;
    width: 8px;
    height: 8px;
    border-radius: 50%;
    margin-right: 8px;
}

.close-btn {
    background: transparent;
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
    padding: 6px 16px;
    cursor: pointer;
    border-radius: 20px;
    transition: all 0.2s;
    font-size: 11px;
    text-transform: uppercase;
    font-weight: 700;
    letter-spacing: 0.5px;
}

.close-btn:hover {
    background: var(--primary-color);
    color: #000;
    box-shadow: 0 0 10px rgba(0, 255, 255, 0.4);
}

.min-btn {
    background: transparent;
    border: none;
    color: var(--text-dim);
    width: 32px;
    height: 32px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: all 0.2s;
    font-size: 20px;
}

.min-btn:hover {
    color: #fff;
    background: rgba(255, 255, 255, 0.1);
}

/* Cursor */
#cursor {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 20px;
    height: 20px;
    border: 2px solid rgba(255, 255, 255, 0.5);
    border-radius: 50%;
    transform: translate(-50%, -50%);
    pointer-events: none;
    transition: transform 0.15s ease-out, border-color 0.2s;
    mix-blend-mode: difference;
    z-index: 50;
    display: none;
}

@media (hover: hover) {
    #cursor {
        display: block;
    }
}

#loading {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: #000;
    color: var(--primary-color);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 24px;
    z-index: 999;
    letter-spacing: 5px;
    font-weight: 300;
    transition: opacity 1s;
}

#inspect-hint {
    position: absolute;
    bottom: 40px;
    left: 50%;
    transform: translateX(-50%);
    color: rgba(255, 255, 255, 0.9);
    background: rgba(0, 0, 0, 0.4);
    backdrop-filter: blur(8px);
    padding: 12px 30px;
    border-radius: 30px;
    border: 1px solid rgba(255, 255, 255, 0.2);
    display: none;
    font-size: 13px;
    pointer-events: none;
    text-transform: uppercase;
    letter-spacing: 2px;
    font-weight: 600;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
    white-space: nowrap;
}

/* FOCUS MODE BACK BUTTON */
#focus-back-btn {
    position: absolute;
    top: 30px;
    left: 50%;
    transform: translateX(-50%);
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(10px);
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
    padding: 12px 32px;
    cursor: pointer;
    border-radius: 40px;
    font-size: 14px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    pointer-events: auto;
    display: none;
    z-index: 400;
    box-shadow: 0 0 20px rgba(0, 255, 255, 0.1);
    transition: all 0.3s;
}

#focus-back-btn:hover {
    background: var(--primary-color);
    color: #000;
    box-shadow: 0 0 30px rgba(0, 255, 255, 0.4);
    padding: 12px 40px;
}

/* CARD GAME OVERLAY */
#card-game-container {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(5, 8, 15, 0.95);
    backdrop-filter: blur(20px);
    z-index: 300;
    display: none;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    pointer-events: auto;
    overflow-y: auto;
    padding-top: 60px;
}

.game-header {
    color: #fff;
    font-size: 32px;
    font-weight: 800;
    margin-top: 0;
    margin-bottom: 30px;
    text-transform: uppercase;
    letter-spacing: 2px;
    text-align: center;
}

.card-grid {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 16px;
    max-width: 800px;
    padding: 20px;
    margin-bottom: 20px;
}

.memory-card {
    width: 100px;
    height: 140px;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.6s cubic-bezier(0.4, 0.0, 0.2, 1);
    cursor: pointer;
}

.memory-card.flip {
    transform: rotateY(180deg);
}

.memory-card .front-face,
.memory-card .back-face {
    width: 100%;
    height: 100%;
    position: absolute;
    backface-visibility: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 12px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.5);
    text-align: center;
    padding: 4px;
    box-sizing: border-box;
    font-size: 11px;
    font-weight: 700;
}

.memory-card .front-face {
    background: linear-gradient(135deg, #101025, #0a0a15);
    border: 2px solid rgba(0, 255, 255, 0.3);
    color: #fff;
    transform: rotateY(180deg);
    display: flex;
    flex-direction: column;
    justify-content: center;
    box-shadow: inset 0 0 20px rgba(0, 255, 255, 0.05);
    /* Subtle inner glow */
}

/* Card Hover Effect */
.memory-card:hover {
    transform: scale(1.05);
    z-index: 10;
}

.memory-card.flip:hover {
    transform: rotateY(180deg) scale(1.05);
}

.memory-card .back-face {
    background: linear-gradient(135deg, #00ffff, #0088ff);
    border: 2px solid rgba(255, 255, 255, 0.6);
    font-size: 14px;
    color: #000;
    font-weight: 800;
    text-shadow: none;
    display: flex;
    align-items: center;
    justify-content: center;
    word-break: break-all;
    box-shadow: 0 0 15px rgba(0, 255, 255, 0.4);
}

/* MATCHED ANIMATION */
.memory-card.matched .front-face {
    background: linear-gradient(135deg, #004411, #002200);
    border-color: #00ff66;
    animation: matchPulse 1s ease-out;
    box-shadow: 0 0 20px rgba(0, 255, 100, 0.3);
}

@keyframes matchPulse {
    0% {
        transform: rotateY(180deg) scale(1);
        box-shadow: 0 0 0 rgba(0, 255, 100, 0.6);
        border-color: #00ff66;
    }

    50% {
        transform: rotateY(180deg) scale(1.1);
        box-shadow: 0 0 30px rgba(0, 255, 100, 0.8);
        border-color: #fff;
    }

    100% {
        transform: rotateY(180deg) scale(1);
        box-shadow: 0 0 20px rgba(0, 255, 100, 0.3);
        border-color: #00ff66;
    }
}

.play-again-btn {
    background: #00ff66;
    color: #003311;
    border: none;
    padding: 16px 40px;
    font-size: 16px;
    font-weight: 800;
    border-radius: 40px;
    cursor: pointer;
    margin-top: 10px;
    margin-bottom: 30px;
    display: none;
    box-shadow: 0 0 30px rgba(0, 255, 100, 0.4);
    animation: pulse 1.5s infinite;
    text-transform: uppercase;
    letter-spacing: 1px;
    font-family: 'Outfit', sans-serif;
}

@keyframes pulse {
    0% {
        transform: scale(1);
        box-shadow: 0 0 20px rgba(0, 255, 100, 0.4);
    }

    50% {
        transform: scale(1.05);
        box-shadow: 0 0 40px rgba(0, 255, 100, 0.6);
    }

    100% {
        transform: scale(1);
        box-shadow: 0 0 20px rgba(0, 255, 100, 0.4);
    }
}

/* GRAVITY QUIZ UI */
#gravity-quiz-ui {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: auto;
    z-index: 300;
    display: none;
    flex-direction: column;
    justify-content: space-between;
    align-items: center;
    padding: 30px;
    box-sizing: border-box;
    background: transparent;
}

#quiz-hud {
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    pointer-events: auto;
    background: rgba(0, 0, 0, 0.6);
    /* Background only for HUD */
    backdrop-filter: blur(10px);
    padding: 15px 30px;
    border-radius: 16px;
    border: 1px solid rgba(255, 255, 255, 0.1);
}

#quiz-score {
    font-size: 28px;
    font-weight: 800;
    color: #00ff66;
    text-shadow: 0 0 20px rgba(0, 255, 100, 0.4);
}

.quiz-header-bg {
    background: rgba(0, 0, 0, 0.6);
    padding: 20px 40px;
    border-radius: 16px;
    border: 1px solid rgba(0, 255, 255, 0.2);
    margin-top: 20px;
    backdrop-filter: blur(10px);
    pointer-events: auto;
    text-align: center;
}

#quiz-options {
    display: flex;
    gap: 20px;
    padding-bottom: 40px;
    pointer-events: auto;
    flex-wrap: wrap;
    justify-content: center;
    width: 100%;
    background: linear-gradient(0deg, rgba(0, 0, 0, 0.8) 0%, transparent 100%);
    padding-top: 40px;
}

.quiz-btn {
    background: rgba(10, 20, 40, 0.6);
    backdrop-filter: blur(10px);
    border: 1px solid var(--primary-color);
    color: #fff;
    padding: 20px 15px;
    font-size: 20px;
    font-family: 'Times New Roman', serif;
    font-style: italic;
    border-radius: 12px;
    cursor: pointer;
    min-width: 180px;
    flex-grow: 1;
    max-width: 320px;
    text-align: center;
    transition: all 0.2s cubic-bezier(0.25, 1, 0.5, 1);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
}

.quiz-btn:hover {
    background: rgba(0, 255, 255, 0.15);
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0, 255, 255, 0.2);
    border-color: #fff;
}

.quiz-btn.wrong {
    background: rgba(255, 0, 0, 0.2);
    border-color: #ff3333;
    box-shadow: 0 0 30px rgba(255, 0, 0, 0.4);
}

.quiz-btn.correct {
    background: rgba(0, 255, 0, 0.2);
    border-color: #00ff66;
    color: #fff;
    box-shadow: 0 0 30px rgba(0, 255, 0, 0.4);
    transform: scale(1.05);
}

.game-exit-btn {
    background: transparent;
    border: 1px solid var(--accent-color);
    color: var(--accent-color);
    padding: 8px 24px;
    cursor: pointer;
    border-radius: 30px;
    font-weight: 700;
    pointer-events: auto;
    text-transform: uppercase;
    font-size: 13px;
    letter-spacing: 1px;
    transition: all 0.2s;
}

.game-exit-btn:hover {
    background: var(--accent-color);
    color: #fff;
    box-shadow: 0 0 15px rgba(255, 0, 255, 0.4);
}

.speed-btn {
    background: transparent;
    border: 1px solid #00ff66;
    color: #00ff66;
    padding: 8px 16px;
    cursor: pointer;
    border-radius: 30px;
    font-weight: 700;
    pointer-events: auto;
    text-transform: uppercase;
    font-size: 13px;
    letter-spacing: 1px;
    transition: all 0.2s;
    min-width: 100px;
}

.speed-btn:hover {
    background: #00ff66;
    color: #000;
    box-shadow: 0 0 15px rgba(0, 255, 100, 0.4);
}

#toast {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: rgba(0, 255, 100, 0.95);
    color: #002200;
    padding: 20px 50px;
    font-size: 24px;
    font-weight: 800;
    border-radius: 50px;
    width: auto;
    display: none;
    z-index: 500;
    box-shadow: 0 0 60px rgba(0, 255, 100, 0.6);
    text-align: center;
}

.mode-btn {
    background: transparent;
    border: 1px solid rgba(255, 255, 255, 0.3);
    color: rgba(255, 255, 255, 0.7);
    padding: 10px 20px;
    margin: 8px;
    cursor: pointer;
    font-size: 13px;
    font-weight: 600;
    border-radius: 30px;
    transition: all 0.2s;
    white-space: nowrap;
    font-family: 'Outfit', sans-serif;
}

.mode-btn.active {
    background: #00ff00;
    border-color: #00ff00;
    color: #000;
    opacity: 1;
    box-shadow: 0 0 15px rgba(255, 255, 255, 0.3);
}

.mode-btn:hover:not(.active) {
    border-color: #fff;
    color: #fff;
    background: rgba(255, 255, 255, 0.1);
}

.top-exit-btn {
    position: absolute;
    top: 30px;
    right: 30px;
    background: rgba(20, 0, 0, 0.4);
    border: 1px solid #ff3333;
    color: #ff3333;
    padding: 10px 24px;
    cursor: pointer;
    border-radius: 5px;
    font-weight: 700;
    pointer-events: auto;
    text-transform: uppercase;
    z-index: 305;
    font-size: 12px;
    letter-spacing: 1px;
    backdrop-filter: blur(5px);
    transition: all 0.2s;
}

.top-exit-btn:hover {
    background: #ff3333;
    color: #fff;
    box-shadow: 0 0 20px rgba(255, 0, 0, 0.4);
}

/* --- MOBILE RESPONSIVE QUERIES --- */
@media (max-width: 768px) {
    #sidebar {
        width: 85%;
        max-width: 320px;
    }

    #sidebar-toggle.active {
        left: 85%;
        margin-left: -55px;
    }

    #info-panel {
        width: 100%;
        right: 0;
    }

    #info-panel.active {
        transform: translateX(0);
    }

    .formula-math {
        font-size: 20px;
    }

    .explanation {
        font-size: 14px;
    }

    #focus-back-btn {
        top: 70px;
        padding: 8px 20px;
        font-size: 14px;
    }

    .card-grid {
        gap: 5px;
    }

    .memory-card {
        width: 70px;
        height: 90px;
    }

    .quiz-btn {
        font-size: 14px;
        padding: 12px 5px;
        width: 45%;
        min-width: auto;
    }

    #gravity-mode-select {
        display: flex;
        flex-wrap: wrap;
        justify-content: center;
    }

    .top-exit-btn {
        padding: 5px 10px;
        font-size: 12px;
    }

    h1 {
        font-size: 20px;
    }
}