:root {
    --bg-color: #0c0e12;
    --text-main: #f8f9fa;
    --text-sub: #94a3b8;
    --accent-1: #6366f1;
    --accent-2: #ec4899;
    --accent-green: #10b981;
    --glass-bg: rgba(255, 255, 255, 0.03);
    --glass-border: rgba(255, 255, 255, 0.08);
    --glass-hover: rgba(255, 255, 255, 0.06);
    --card-bg: rgba(15, 23, 42, 0.6);
}

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

body {
    font-family: 'Outfit', 'Helvetica Neue', Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding: 1rem;
    overflow-x: hidden;
}

.app-container {
    width: 100%;
    max-width: 1200px;
    background: var(--card-bg);
    border: 1px solid var(--glass-border);
    border-radius: 20px;
    padding: 1.2rem;
    backdrop-filter: blur(20px);
    box-shadow: 0 20px 50px rgba(0, 0, 0, 0.4);
}

/* Header styling */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    border-bottom: 1px solid var(--glass-border);
    padding-bottom: 0.8rem;
}

.header-title h1 {
    font-size: 1.5rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 0.1rem;
}

.header-title p {
    font-size: 0.85rem;
    color: var(--text-sub);
}

.back-btn {
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    color: var(--text-main);
    width: 38px;
    height: 38px;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 50%;
    transition: all 0.3s ease;
}

.back-btn:hover {
    background: var(--glass-hover);
    border-color: var(--text-sub);
    transform: scale(1.05);
}

/* Workspace layout */
.workspace {
    display: grid;
    grid-template-columns: 320px 1fr;
    gap: 1.2rem;
}

/* Sidebar / Controls */
.sidebar {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.panel {
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--glass-border);
    border-radius: 14px;
    padding: 1rem;
}

.panel-title {
    font-size: 1rem;
    font-weight: 700;
    margin-bottom: 0.8rem;
    color: var(--text-main);
    border-left: 4px solid var(--accent-1);
    padding-left: 0.5rem;
}

@media (max-width: 968px) {
    .workspace {
        grid-template-columns: 1fr;
        max-width: 100%;
        min-width: 0;
    }
    .sidebar {
        flex-direction: column-reverse;
        max-width: 100%;
        min-width: 0;
    }
    .display-area {
        max-width: 100%;
        min-width: 0;
    }
    .panel {
        padding: 0.8rem;
        max-width: 100%;
        min-width: 0;
    }
    .problem-selector {
        grid-template-columns: repeat(2, minmax(0, 1fr));
        gap: 0.4rem;
    }
    .canvas-container {
        width: 100%;
        height: 480px;
        aspect-ratio: auto;
    }
    .selector-btn {
        font-size: 0.78rem;
        padding: 0.5rem 0.3rem;
    }
    .visualizer-tabs {
        gap: 0.2rem;
        padding-bottom: 0.2rem;
        overflow-x: auto;
        white-space: nowrap;
        scrollbar-width: none; /* Hide scrollbar for clean look */
    }
    .visualizer-tabs::-webkit-scrollbar {
        display: none; /* Hide scrollbar in chrome/safari */
    }
    .tab {
        padding: 0.4rem 0.5rem;
        font-size: 0.75rem;
        white-space: nowrap;
    }
    .recommend-badge {
        font-size: 0.6rem;
        padding: 0.05rem 0.25rem;
        margin-left: 0.2rem;
    }
}

/* Slider Toggle Switch */
.switch {
    position: relative;
    display: inline-block;
    width: 44px;
    height: 24px;
}

.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider-toggle {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(255, 255, 255, 0.05);
    transition: .3s ease;
    border-radius: 24px;
    border: 1px solid var(--glass-border);
}

.slider-toggle:before {
    position: absolute;
    content: "";
    height: 16px;
    width: 16px;
    left: 3px;
    bottom: 3px;
    background-color: var(--text-sub);
    transition: .3s ease;
    border-radius: 50%;
}

input:checked + .slider-toggle {
    background-color: rgba(236, 72, 153, 0.15);
    border-color: var(--accent-2);
}

input:checked + .slider-toggle:before {
    transform: translateX(20px);
    background-color: var(--accent-2);
    box-shadow: 0 0 8px var(--accent-2);
}

/* Refresh button styling */
.refresh-btn {
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    color: var(--text-main);
    padding: 0.4rem 0.8rem;
    border-radius: 8px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.4rem;
    transition: all 0.3s ease;
}

.refresh-btn:hover {
    background: var(--glass-hover);
    border-color: var(--accent-2);
    box-shadow: 0 0 10px rgba(236, 72, 153, 0.2);
}

/* Problem selector buttons */
.problem-selector {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.5rem;
}

.selector-btn {
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    color: var(--text-sub);
    padding: 0.6rem 0.5rem;
    border-radius: 10px;
    font-size: 0.88rem;
    font-weight: 600;
    cursor: pointer;
    text-align: center;
    transition: all 0.3s ease;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.selector-btn:hover {
    background: var(--glass-hover);
    color: var(--text-main);
}

.selector-btn.active {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.2), rgba(236, 72, 153, 0.2));
    border-color: var(--accent-1);
    color: var(--text-main);
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.1);
}

/* Problem Text Panel */
.problem-desc-box {
    font-size: 0.95rem;
    line-height: 1.6;
    color: var(--text-main);
    background: rgba(255, 255, 255, 0.01);
    border: 1px dashed var(--glass-border);
    border-radius: 12px;
    padding: 1rem;
}

/* Main Display Area (Right) */
.display-area {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

/* Visualizer Tabs */
.visualizer-tabs {
    display: flex;
    gap: 0.5rem;
    border-bottom: 1px solid var(--glass-border);
    padding-bottom: 0.5rem;
}

.tab {
    background: none;
    border: none;
    color: var(--text-sub);
    padding: 0.75rem 1.25rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    border-radius: 8px;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
}

.tab:hover {
    color: var(--text-main);
    background: var(--glass-hover);
}

.tab.active {
    color: var(--text-main);
    background: var(--glass-bg);
    box-shadow: inset 0 -2px 0 var(--accent-2);
    border-bottom-left-radius: 0;
    border-bottom-right-radius: 0;
}

/* Recommendation Badge */
.recommend-badge {
    font-size: 0.65rem;
    padding: 0.15rem 0.4rem;
    border-radius: 4px;
    margin-left: 6px;
    font-weight: 800;
    display: inline-block;
    letter-spacing: normal;
}

.recommend-badge.best {
    background: linear-gradient(135deg, #fbbf24, #f59e0b);
    color: #0c0e12;
    box-shadow: 0 0 10px rgba(251, 191, 36, 0.4);
}

.recommend-badge.standard {
    background: linear-gradient(135deg, #10b981, #059669);
    color: #fff;
    box-shadow: 0 0 10px rgba(16, 185, 129, 0.3);
}

/* Canvas Viewport */
.canvas-container {
    position: relative;
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid var(--glass-border);
    border-radius: 16px;
    width: 100%;
    aspect-ratio: 16/10;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
}

canvas {
    display: block;
    width: 100%;
    height: 100%;
}

/* Explanation step text card */
.explanation-panel {
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--glass-border);
    border-radius: 16px;
    padding: 1.5rem;
}

.steps-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.step-item {
    display: flex;
    gap: 1rem;
    align-items: flex-start;
    animation: fadeIn 0.5s ease both;
    padding: 0.75rem;
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.3s ease;
    border: 1px solid transparent;
}

.step-item:hover {
    background: rgba(255, 255, 255, 0.04);
    border-color: var(--glass-border);
}

.step-item.active {
    background: rgba(99, 102, 241, 0.08);
    border-color: rgba(99, 102, 241, 0.3);
    box-shadow: 0 4px 20px rgba(99, 102, 241, 0.05);
}

.step-num {
    background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
    color: #fff;
    font-size: 0.85rem;
    font-weight: 800;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-shrink: 0;
    transition: all 0.3s ease;
}

.step-item.active .step-num {
    background: linear-gradient(135deg, var(--accent-2), var(--accent-1));
    transform: scale(1.1);
}

.step-content {
    font-size: 0.95rem;
    line-height: 1.6;
    color: var(--text-main);
}

.step-formula {
    font-family: 'Courier New', Courier, monospace;
    background: rgba(255, 255, 255, 0.05);
    padding: 0.2rem 0.4rem;
    border-radius: 4px;
    color: var(--accent-2);
    font-weight: 600;
    margin-top: 0.25rem;
    display: inline-block;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Tooltip Help styling */
.help-btn {
    background: rgba(255,255,255,0.08);
    border: 1px solid rgba(255,255,255,0.15);
    color: #fbbf24;
    border-radius: 50%;
    width: 24px;
    height: 24px;
    font-size: 13px;
    font-weight: bold;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s;
}

.help-btn:hover {
    background: rgba(251, 191, 36, 0.15);
    border-color: #fbbf24;
    box-shadow: 0 0 8px rgba(251, 191, 36, 0.3);
}

.tooltip-content {
    visibility: hidden;
    width: 280px;
    background-color: #1e293b;
    color: #f8f9fa;
    text-align: left;
    border: 1px solid rgba(251, 191, 36, 0.4);
    border-radius: 12px;
    padding: 1rem;
    position: absolute;
    z-index: 10;
    top: 125%;
    right: 0;
    opacity: 0;
    font-size: 0.85rem;
    line-height: 1.5;
    transition: opacity 0.3s, visibility 0.3s;
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.6);
}

.tooltip-content::after {
    content: "";
    position: absolute;
    bottom: 100%;
    right: 8px;
    border-width: 6px;
    border-style: solid;
    border-color: transparent transparent #1e293b transparent;
}

.tooltip-container:hover .tooltip-content {
    visibility: visible;
    opacity: 1;
}

/* Step Learner Controls Styling */
.step-learner-controls {
    position: absolute;
    top: 12px;
    right: 12px;
    background: rgba(12, 14, 18, 0.75);
    backdrop-filter: blur(12px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: 20px;
    padding: 4px 8px;
    display: flex;
    align-items: center;
    gap: 8px;
    z-index: 5;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
    user-select: none;
}

.learner-btn {
    background: rgba(255, 255, 255, 0.08);
    border: 1px solid rgba(255, 255, 255, 0.15);
    color: var(--text-main);
    border-radius: 50%;
    width: 28px;
    height: 28px;
    font-size: 11px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
}

.learner-btn:hover {
    background: var(--accent-1);
    border-color: var(--accent-1);
    box-shadow: 0 0 8px var(--accent-1);
}

.learner-status {
    color: var(--text-main);
    font-size: 0.75rem;
    font-weight: 700;
    min-width: 90px;
    text-align: center;
}

/* Floating Drag Balloon Styling */
.canvas-balloon {
    position: absolute;
    bottom: 25px;
    left: 50%;
    transform: translateX(-50%);
    width: 290px;
    background: rgba(12, 18, 28, 0.55);
    backdrop-filter: blur(8px);
    border: 1.5px solid var(--accent-1);
    border-radius: 14px;
    padding: 14px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.55), 0 0 15px rgba(99, 102, 241, 0.25);
    z-index: 8;
    cursor: move;
    user-select: none;
    transition: opacity 0.3s ease;
    opacity: 0;
    pointer-events: none; /* Initially hidden / clicks pass through until active */
}

.canvas-balloon.active {
    opacity: 1;
    pointer-events: auto;
}

.balloon-close {
    position: absolute;
    top: 6px;
    right: 8px;
    background: none;
    border: none;
    color: var(--text-sub);
    font-size: 16px;
    font-weight: bold;
    cursor: pointer;
    line-height: 1;
    transition: color 0.2s;
}

.balloon-close:hover {
    color: var(--accent-2);
}

.balloon-text {
    font-size: 0.82rem;
    line-height: 1.5;
    color: var(--text-main);
    padding-right: 14px; /* leave room for close button */
    word-break: break-all;
}

.balloon-formula {
    font-family: 'Courier New', Courier, monospace;
    background: rgba(255, 255, 255, 0.05);
    padding: 4px 8px;
    border-radius: 6px;
    color: var(--accent-2);
    font-weight: 600;
    font-size: 0.78rem;
    margin-top: 8px;
    display: inline-block;
}

#canvas-help-balloon {
    background: #0f172a; /* Fully opaque background */
    backdrop-filter: none;
    border-color: #fbbf24;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.55), 0 0 15px rgba(251, 191, 36, 0.25);
}