/* --------------------------------------------------
   LAW OF UNIVERSAL GRAVITATION VIRTUAL LAB STYLESHEET
   -------------------------------------------------- */

:root {
    /* Color Palette */
    --bg-main: #0b0f19;
    --bg-card: #151c2c;
    --bg-card-header: #1e293b;
    --bg-input: #0f172a;
    
    --border-color: #334155;
    --border-focus: #3b82f6;

    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;

    /* Theme Accents */
    --color-m1: #3b82f6;
    --color-m1-light: #93c5fd;
    --color-m2: #f59e0b;
    --color-m2-light: #fde68a;
    --color-dist: #38bdf8;
    --color-force: #ef4444;
    --color-success: #10b981;

    /* Fonts */
    --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;

    /* Border Radius & Shadows */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --shadow-card: 0 10px 25px -5px rgba(0, 0, 0, 0.4), 0 8px 10px -6px rgba(0, 0, 0, 0.3);
}

/* Reset & Base Setup */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    background-color: var(--bg-main);
    color: var(--text-primary);
    font-family: var(--font-sans);
    line-height: 1.5;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    overflow-x: hidden;
}

/* Header */
.lab-header {
    background-color: var(--bg-card);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 1.5rem;
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-container {
    max-width: 1440px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.header-title h1 {
    font-size: 1.35rem;
    font-weight: 700;
    color: #ffffff;
    letter-spacing: -0.02em;
}

.badge {
    display: inline-block;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    color: var(--color-dist);
    background: rgba(56, 189, 248, 0.1);
    padding: 0.15rem 0.6rem;
    border-radius: 9999px;
    border: 1px solid rgba(56, 189, 248, 0.3);
    margin-top: 0.25rem;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.mode-selector {
    display: flex;
    background: var(--bg-input);
    padding: 3px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
}

.btn {
    font-family: var(--font-sans);
    font-size: 0.85rem;
    font-weight: 600;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    border: none;
    cursor: pointer;
    transition: all 0.2s ease;
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
}

.btn-mode {
    background: transparent;
    color: var(--text-secondary);
}

.btn-mode:hover {
    color: var(--text-primary);
}

.btn-mode.active {
    background: var(--color-m1);
    color: #ffffff;
    box-shadow: 0 2px 8px rgba(59, 130, 246, 0.4);
}

.btn-reset {
    background: rgba(239, 68, 68, 0.15);
    color: #fca5a5;
    border: 1px solid rgba(239, 68, 68, 0.4);
}

.btn-reset:hover {
    background: rgba(239, 68, 68, 0.3);
    color: #ffffff;
}

.btn-primary {
    background: var(--color-m1);
    color: #ffffff;
}

.btn-primary:hover {
    background: #2563eb;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.4);
}

.btn-success {
    background: var(--color-success);
    color: #ffffff;
}

.btn-success:hover {
    background: #059669;
    box-shadow: 0 4px 12px rgba(16, 185, 129, 0.4);
}

.btn-secondary {
    background: var(--bg-input);
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--border-color);
    color: var(--text-primary);
}

.btn-sm {
    padding: 0.3rem 0.75rem;
    font-size: 0.8rem;
}

/* Main Layout Grid */
.main-layout {
    max-width: 1440px;
    width: 100%;
    margin: 1.5rem auto;
    padding: 0 1.5rem;
    display: grid;
    grid-template-columns: 1fr 380px;
    gap: 1.5rem;
}

.graph-card, .table-card, .edu-card {
    grid-column: 1 / -1;
}

/* Cards Design */
.card, .sim-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-card);
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.card-header {
    padding: 1rem 1.25rem;
    background-color: var(--bg-card-header);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 0.75rem;
}

.card-header h2, .card h3 {
    font-size: 1.1rem;
    font-weight: 600;
    color: #ffffff;
}

.title-with-subtitle {
    display: flex;
    flex-direction: column;
}

.subtitle {
    font-size: 0.8rem;
    color: var(--text-secondary);
    font-weight: 400;
}

.card-header-sm {
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.live-tag {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    font-weight: 700;
    color: var(--color-success);
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
}

.pulse-dot {
    width: 8px;
    height: 8px;
    background-color: var(--color-success);
    border-radius: 50%;
    box-shadow: 0 0 8px var(--color-success);
    animation: pulse 1.5s infinite;
}

@keyframes pulse {
    0% { opacity: 0.4; transform: scale(0.9); }
    50% { opacity: 1; transform: scale(1.15); }
    100% { opacity: 0.4; transform: scale(0.9); }
}

/* Toggle Switch */
.header-toggles {
    display: flex;
    align-items: center;
}

.toggle-container {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    font-size: 0.825rem;
    color: var(--text-secondary);
    user-select: none;
}

.toggle-container input {
    display: none;
}

.toggle-slider {
    width: 36px;
    height: 20px;
    background-color: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    position: relative;
    transition: 0.3s;
}

.toggle-slider::before {
    content: "";
    position: absolute;
    top: 2px;
    left: 2px;
    width: 14px;
    height: 14px;
    background-color: var(--text-secondary);
    border-radius: 50%;
    transition: 0.3s;
}

.toggle-container input:checked + .toggle-slider {
    background-color: var(--color-m1);
    border-color: var(--color-m1);
}

.toggle-container input:checked + .toggle-slider::before {
    transform: translateX(16px);
    background-color: #ffffff;
}

.toggle-container input:checked ~ .toggle-label {
    color: var(--text-primary);
}

/* SVG Simulation Apparatus */
.svg-container {
    width: 100%;
    background-color: #080c15;
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 420px;
    touch-action: none;
}

.svg-container svg {
    width: 100%;
    height: 100%;
    max-height: 520px;
    display: block;
}

.draggable-mass {
    transition: filter 0.2s ease;
}

.draggable-mass:hover {
    filter: drop-shadow(0 0 10px rgba(96, 165, 250, 0.5));
}

.draggable-mass:active {
    cursor: grabbing;
}

/* Right Controls & Measurements Column */
.controls-column {
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
}

/* Metrics Dashboard */
.measurements-card {
    padding: 0;
}

.metrics-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.75rem;
    padding: 1rem;
}

.metric-box {
    background-color: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 0.75rem 0.9rem;
    display: flex;
    flex-direction: column;
}

.metric-label {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.metric-value {
    font-family: var(--font-mono);
    font-size: 1.1rem;
    font-weight: 700;
    color: #ffffff;
    margin-top: 0.2rem;
}

.metric-value small {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-muted);
}

.box-m1 .metric-value { color: var(--color-m1-light); }
.box-m2 .metric-value { color: var(--color-m2-light); }
.box-dist .metric-value { color: var(--color-dist); }

.highlight-force {
    grid-column: 1 / -1;
    background: linear-gradient(135deg, rgba(239, 68, 68, 0.1) 0%, rgba(15, 23, 42, 0.8) 100%);
    border-color: rgba(239, 68, 68, 0.4);
}

.highlight-force .metric-value {
    font-size: 1.4rem;
    color: #fca5a5;
}

.force-subtext {
    font-size: 0.7rem;
    color: var(--text-muted);
    font-family: var(--font-mono);
    margin-top: 0.25rem;
}

/* Controls Form Card */
.controls-card {
    padding: 1.25rem;

    gap: 1.25rem;
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.control-label-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.control-label-row label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-primary);
}

.input-with-unit {
    display: inline-flex;
    align-items: center;
    background-color: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 0.2rem 0.5rem;
}

.input-with-unit input {
    width: 65px;
    background: transparent;
    border: none;
    outline: none;
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 0.9rem;
    font-weight: 600;
    text-align: right;
}

.input-with-unit input::-webkit-inner-spin-button {
    opacity: 0.5;
}

.input-with-unit .unit {
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-left: 0.3rem;
    font-family: var(--font-mono);
}

/* Range Sliders */
.slider {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 8px;
    background: var(--bg-input);
    border-radius: 4px;
    outline: none;
    border: 1px solid var(--border-color);
    cursor: pointer;
}

.slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: #ffffff;
    cursor: pointer;
    box-shadow: 0 0 8px rgba(0, 0, 0, 0.5);
    transition: transform 0.1s ease;
}

.slider::-webkit-slider-thumb:hover {
    transform: scale(1.15);
}

.slider-m1::-webkit-slider-thumb { background: var(--color-m1); }
.slider-m2::-webkit-slider-thumb { background: var(--color-m2); }
.slider-dist::-webkit-slider-thumb { background: var(--color-dist); }

.range-limits {
    display: flex;
    justify-content: space-between;
    font-size: 0.7rem;
    color: var(--text-muted);
    font-family: var(--font-mono);
}

/* Control Actions */
.control-actions {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.75rem;
    margin-top: 0.5rem;
}

/* Verification Banner */
.verification-banner {
    background: rgba(16, 185, 129, 0.1);
    border: 1px solid rgba(16, 185, 129, 0.4);
    border-radius: var(--radius-md);
    padding: 0.85rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    animation: fadeIn 0.3s ease;
}

.verification-banner.hidden {
    display: none;
}

.verify-header {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--color-success);
    font-weight: 700;
    font-size: 0.9rem;
}

.verify-icon {
    font-size: 1.1rem;
    background: var(--color-success);
    color: #ffffff;
    width: 22px;
    height: 22px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.verify-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.verify-list li {
    font-size: 0.78rem;
    color: var(--text-secondary);
    display: flex;
    align-items: flex-start;
    gap: 0.4rem;
}

.verify-list li::before {
    content: "✓";
    color: var(--color-success);
    font-weight: bold;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(-5px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Canvas Graph Section */
.canvas-wrapper {
    padding: 1.25rem;
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    background: #090d16;
}

#graphCanvas {
    max-width: 100%;
    height: auto;
    background-color: #0f172a;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
}

.graph-legend {
    padding: 0.75rem 1.25rem;
    background-color: var(--bg-card-header);
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: center;
    gap: 2rem;
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.legend-item {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.legend-line {
    width: 24px;
    height: 2px;
    display: inline-block;
}

.line-theory {
    border-top: 2px dashed var(--color-m1);
}

.legend-dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
    display: inline-block;
}

.dot-sample {
    background-color: var(--color-force);
    box-shadow: 0 0 6px var(--color-force);
}

/* Observation Table Section */
.table-wrapper {
    overflow-x: auto;
    padding: 0;
}

.observation-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.85rem;
    text-align: left;
}

.observation-table th {
    background-color: var(--bg-card-header);
    color: var(--text-secondary);
    font-weight: 600;
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--border-color);
    white-space: nowrap;
}

.observation-table td {
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--border-color);
    font-family: var(--font-mono);
    color: var(--text-primary);
}

.observation-table tbody tr:hover {
    background-color: rgba(255, 255, 255, 0.02);
}

.empty-msg {
    text-align: center;
    color: var(--text-muted);
    font-family: var(--font-sans);
    padding: 2rem !important;
}

/* Educational Card Section */
.edu-card {
    padding: 1.5rem;
}

.edu-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
}

.edu-block h3 {
    font-size: 1rem;
    color: var(--color-dist);
    margin-bottom: 0.6rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 0.4rem;
}

.edu-block p {
    font-size: 0.875rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.formula-box {
    background-color: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 0.75rem;
    text-align: center;
    margin: 0.75rem 0;
}

.formula {
    font-family: var(--font-mono);
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--color-m2-light);
}

.edu-list, .procedure-list {
    margin-left: 1.2rem;
    font-size: 0.85rem;
    color: var(--text-secondary);
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.procedure-list li {
    line-height: 1.5;
}

/* Footer */
.lab-footer {
    text-align: center;
    padding: 1.5rem;
    margin-top: auto;
    border-top: 1px solid var(--border-color);
    font-size: 0.8rem;
    color: var(--text-muted);
    background-color: var(--bg-card);
}

/* RESPONSIVE DESIGN BREAKPOINTS */
@media (max-width: 1080px) {
    .main-layout {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 640px) {
    .lab-header {
        padding: 0.75rem 1rem;
    }

    .header-container {
        flex-direction: column;
        align-items: flex-start;
    }

    .header-actions {
        width: 100%;
        justify-content: space-between;
    }

    .mode-selector {
        flex-wrap: wrap;
        width: 100%;
    }

    .btn-mode {
        flex: 1;
        text-align: center;
        justify-content: center;
        padding: 0.4rem 0.5rem;
        font-size: 0.75rem;
    }

    .metrics-grid {
        grid-template-columns: 1fr;
    }

    .control-actions {
        grid-template-columns: 1fr;
    }

    .svg-container {
        min-height: 320px;
    }
}