:root {
    --bg-dark: #0f172a;
    --bg-gradient: radial-gradient(circle at 50% 50%, #1e293b 0%, #0f172a 100%);
    --glass-bg: linear-gradient(180deg, rgba(255, 255, 255, 0.95) 0%, rgba(255, 240, 245, 0.9) 100%);
    --glass-border: rgba(255, 255, 255, 0.9);
    --accent-magenta: #EE0058;
    --accent-magenta-hover: #ff3377;
    --text-dark: #1e293b;
    --text-muted: #64748b;
}

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

html, body {
    margin: 0;
    width: 100vw;
    height: 100vh;
    overflow: hidden;
    font-family: 'JetBrains Mono', monospace;
    background: var(--bg-gradient);
    color: #fff;
    display: flex;
}

/* --- Aero Sidebar Navigation --- */
.aero-sidebar {
    width: 260px;
    min-width: 260px;
    height: 100vh;
    background: linear-gradient(90deg, rgba(255,255,255,0.1) 0%, rgba(255,255,255,0.03) 100%);
    backdrop-filter: blur(20px);
    border-right: 2px solid rgba(255,255,255,0.15);
    display: flex;
    flex-direction: column;
    padding: 25px 15px;
    box-shadow: 5px 0 25px rgba(0,0,0,0.2);
    z-index: 50;
}

.sidebar-brand {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 30px;
    padding-left: 10px;
}

.sidebar-brand h2 {
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.6rem;
    font-weight: 900;
    color: #fff;
    text-shadow: 0 0 12px rgba(238, 0, 88, 0.7);
}

.nav-stack {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.nav-btn {
    background: rgba(255, 255, 255, 0.08);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 8px;
    color: #fff;
    padding: 12px 16px;
    font-weight: bold;
    font-size: 0.95rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 12px;
    transition: all 0.2s ease;
    font-family: 'JetBrains Mono', monospace;
}

.nav-btn:hover, .nav-btn.active {
    background: linear-gradient(180deg, var(--accent-magenta-hover) 0%, var(--accent-magenta) 100%);
    border-color: #ff80ab;
    box-shadow: 0 4px 15px rgba(238, 0, 88, 0.4);
    color: #ffffff;
    transform: translateY(-1px);
}

/* --- Main Viewport --- */
.workspace-wrapper {
    flex: 1;
    height: 100vh;
    padding: 25px 35px;
    display: flex;
    flex-direction: column;
    overflow-y: auto;
}

.view-panel {
    display: none;
    width: 100%;
    max-width: 1000px;
    margin: 0 auto;
    height: 100%;
    flex-direction: column;
}

.view-panel.active {
    display: flex;
}

.panel-card {
    background: var(--glass-bg);
    border: 2px solid var(--glass-border);
    border-radius: 14px;
    padding: 24px;
    color: var(--text-dark);
    box-shadow: 0 15px 45px rgba(0,0,0,0.25);
    backdrop-filter: blur(12px);
}

.panel-title {
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.3rem;
    font-weight: 800;
    color: var(--accent-magenta);
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    gap: 8px;
    text-transform: uppercase;
}

/* --- Mode: Homepage --- */
.grid-modes {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.mode-card {
    background: linear-gradient(180deg, rgba(255,255,255,0.9) 0%, rgba(255,240,245,0.7) 100%);
    border: 2px solid rgba(255,255,255,0.9);
    border-radius: 12px;
    padding: 20px;
    cursor: pointer;
    transition: all 0.2s ease;
    color: var(--text-dark);
    box-shadow: 0 8px 20px rgba(0,0,0,0.1);
}

.mode-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 25px rgba(238, 0, 88, 0.35);
    border-color: var(--accent-magenta);
}

.mode-card h3 {
    font-family: 'JetBrains Mono', monospace;
    color: var(--accent-magenta);
    margin-bottom: 8px;
}

/* --- Inputs & Controls --- */
.input-group {
    display: flex;
    gap: 10px;
    margin-bottom: 15px;
}

input[type="text"], textarea {
    flex: 1;
    padding: 10px 14px;
    border: 1px solid #cbd5e1;
    border-radius: 8px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 14px;
    outline: none;
    background: rgba(255, 255, 255, 0.8);
}

input[type="text"]:focus, textarea:focus {
    border-color: var(--accent-magenta);
    box-shadow: 0 0 0 2px rgba(238, 0, 88, 0.2);
}

.action-btn {
    background: linear-gradient(180deg, var(--accent-magenta-hover) 0%, var(--accent-magenta) 100%);
    border: 1px solid #ff80ab;
    border-radius: 8px;
    color: #fff;
    padding: 10px 18px;
    font-family: 'JetBrains Mono', monospace;
    font-weight: 800;
    cursor: pointer;
    box-shadow: 0 4px 10px rgba(238, 0, 88, 0.25);
    transition: transform 0.1s;
}

.action-btn:active {
    transform: scale(0.96);
}

/* --- Mode Specifics --- */
#plotter {
    flex: 1;
    min-width: 0;
    width: 100%;
    height: auto;
    align-self: stretch;
    background: #ffffff;
    border-radius: 8px;
    border: 1px solid #cbd5e1;
    overflow: hidden;
    position: relative;
}

.latex-output {
    min-height: 150px;
    padding: 20px;
    background: #ffffff;
    border-radius: 8px;
    border: 1px solid #cbd5e1;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    color: #1e293b;
}

/* Calculator Keypad */
.calc-display {
    width: 100%;
    height: 60px;
    background: #ffffff;
    border: 1px solid #cbd5e1;
    border-radius: 8px;
    margin-bottom: 15px;
    text-align: right;
    padding: 10px 15px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.8rem;
    color: #1e293b;
}

.calc-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

.calc-btn {
    padding: 16px;
    background: linear-gradient(180deg, #ffffff 0%, #f1f5f9 100%);
    border: 1px solid #cbd5e1;
    border-radius: 8px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.2rem;
    font-weight: bold;
    color: #334155;
    cursor: pointer;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
    transition: all 0.1s ease;
}

.calc-btn:hover {
    background: #e2e8f0;
    color: var(--accent-magenta);
}

.calc-btn.op-btn {
    background: linear-gradient(180deg, #fff0f5 0%, #ffe4e9 100%);
    color: var(--accent-magenta);
    border-color: #fbcfe8;
}

/* --- Graph Mode Split Layout --- */
.graph-workspace {
    display: flex;
    flex-direction: column;
    height: 100%;
}

.graph-container {
    display: flex;
    gap: 15px;
    height: 480px;
}

.expressions-sidebar {
    width: 320px;
    min-width: 320px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    background: rgba(255, 255, 255, 0.6);
    border: 1px solid #cbd5e1;
    border-radius: 8px;
    padding: 12px;
    overflow-y: auto;
}

#expressions-list {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.expr-row {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 8px;
    background: #ffffff;
    border: 1px solid #cbd5e1;
    border-radius: 8px;
    padding: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.03);
    transition: border-color 0.15s;
}

.expr-row:focus-within {
    border-color: var(--accent-magenta);
    box-shadow: 0 0 0 2px rgba(238, 0, 88, 0.15);
}

.expr-color-badge {
    width: 18px;
    height: 18px;
    border-radius: 50%;
    flex-shrink: 0;
    cursor: pointer;
    border: 2px solid rgba(255, 255, 255, 0.8);
    box-shadow: 0 2px 4px rgba(0,0,0,0.15);
    transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.expr-color-badge:hover {
    transform: scale(1.15);
    box-shadow: 0 0 0 2px var(--accent-magenta);
}

.expr-input {
    flex: 1;
    border: none !important;
    outline: none !important;
    background: transparent !important;
    padding: 0 !important;
    box-shadow: none !important;
}

.expr-remove-btn {
    background: transparent;
    border: none;
    color: #94a3b8;
    font-size: 1.1rem;
    font-weight: bold;
    cursor: pointer;
    padding: 0 4px;
    line-height: 1;
}

.expr-remove-btn:hover {
    color: var(--accent-magenta);
}

.add-expr-btn {
    background: linear-gradient(180deg, #ffffff 0%, #f1f5f9 100%);
    border: 1px dashed #cbd5e1;
    border-radius: 8px;
    color: var(--text-dark);
    font-family: 'JetBrains Mono', monospace;
    font-weight: bold;
    padding: 10px;
    cursor: pointer;
    text-align: center;
    transition: all 0.15s ease;
}

.add-expr-btn:hover {
    border-color: var(--accent-magenta);
    color: var(--accent-magenta);
    background: #fff0f5;
}

/* Floating Popover */
.style-popover {
    position: absolute;
    width: 250px;
    max-height: 480px;
    overflow-y: auto;
    background: #ffffff;
    border: 2px solid var(--accent-magenta);
    border-radius: 10px;
    padding: 12px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.2);
    z-index: 100;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.style-popover.hidden {
    display: none;
}

.popover-header {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.85rem;
    font-weight: 800;
    color: var(--accent-magenta);
    border-bottom: 1px solid #e2e8f0;
    padding-bottom: 4px;
}

.popover-section {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.popover-section label {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    font-weight: bold;
    color: var(--text-muted);
}

.preset-row {
    display: flex;
    gap: 6px;
}

.preset-swatch {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    cursor: pointer;
    box-shadow: inset 0 0 0 1px rgba(0,0,0,0.1);
    transition: transform 0.1s;
}

.preset-swatch:hover {
    transform: scale(1.2);
}

.setting-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 4px;
}

/* Custom Stylized Checkbox */
.delta-checkbox {
    position: relative;
    display: inline-block;
    width: 18px;
    height: 18px;
    cursor: pointer;
}

.delta-checkbox input {
    opacity: 0;
    width: 0;
    height: 0;
}

.checkmark {
    position: absolute;
    top: 0;
    left: 0;
    height: 18px;
    width: 18px;
    background-color: #f1f5f9;
    border: 1px solid #cbd5e1;
    border-radius: 4px;
    transition: all 0.2s ease;
}

.delta-checkbox:hover input ~ .checkmark {
    border-color: var(--accent-magenta);
}

.delta-checkbox input:checked ~ .checkmark {
    background-color: var(--accent-magenta);
    border-color: var(--accent-magenta);
}

.checkmark:after {
    content: "";
    position: absolute;
    display: none;
    left: 5px;
    top: 2px;
    width: 4px;
    height: 8px;
    border: solid white;
    border-width: 0 2px 2px 0;
    transform: rotate(45deg);
}

.delta-checkbox input:checked ~ .checkmark:after {
    display: block;
}

.delta-select {
    width: 100%;
    padding: 6px 10px;
    border: 1px solid #cbd5e1;
    border-radius: 6px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
    color: var(--text-dark);
    background: #ffffff;
    outline: none;
    cursor: pointer;
}

.delta-select:focus {
    border-color: var(--accent-magenta);
}

input[type="color"] {
    width: 100%;
    height: 32px;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    background: transparent;
}

input[type="range"] {
    accent-color: var(--accent-magenta);
    cursor: pointer;
}

/* --- Row extras: sliders, list/set chips, errors (under each expression) --- */
.expr-extra {
    flex-basis: 100%;
    display: flex;
    flex-direction: column;
    gap: 4px;
    padding: 2px 4px 0 26px;
    font-size: 0.75rem;
    color: var(--text-muted);
}

.expr-extra[hidden],
.expr-extra [hidden] {
    display: none;
}

.expr-slider-row {
    display: flex;
    align-items: center;
    gap: 8px;
}

.expr-slider {
    flex: 1;
    min-width: 0;
}

.expr-slider:disabled {
    cursor: default;
    opacity: 0.55;
}

.expr-slider-bound {
    font-size: 0.7rem;
    color: #94a3b8;
    min-width: 2ch;
    text-align: center;
}

.expr-computed {
    font-weight: bold;
    color: var(--accent-magenta);
}

.expr-chip {
    align-self: flex-start;
    padding: 2px 8px;
    border-radius: 999px;
    font-weight: bold;
    font-size: 0.7rem;
    color: #fff;
    background: linear-gradient(180deg, #38bdf8 0%, #0284c7 100%);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.5), 0 1px 3px rgba(2, 132, 199, 0.35);
}

.expr-chip-set {
    background: linear-gradient(180deg, #c084fc 0%, #7e22ce 100%);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.5), 0 1px 3px rgba(126, 34, 206, 0.35);
}

.expr-chip-polygon {
    background: linear-gradient(180deg, #34d399 0%, #059669 100%);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.5), 0 1px 3px rgba(5, 150, 105, 0.35);
}

.expr-chip-preview {
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.expr-error {
    color: #b45309;
    font-weight: bold;
}

.expr-add-slider-btn {
    align-self: flex-start;
    background: linear-gradient(180deg, #fff0f5 0%, #ffe4e9 100%);
    border: 1px solid #fbcfe8;
    border-radius: 6px;
    color: var(--accent-magenta);
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    font-weight: bold;
    padding: 3px 8px;
    cursor: pointer;
}

.expr-add-slider-btn:hover {
    border-color: var(--accent-magenta);
}

/* --- Equations in Computer Modern (KaTeX's fonts are Computer Modern) --- */
.mq-math-mode,
.mq-math-mode .mq-nonSymbola,
.mq-math-mode .mq-text-mode,
.mq-math-mode .mq-operator-name {
    font-family: KaTeX_Main, 'Latin Modern Roman', 'CMU Serif', 'Times New Roman', serif;
}

.mq-math-mode var {
    font-family: KaTeX_Math, KaTeX_Main, 'Times New Roman', serif;
}

.mq-math-mode var.mq-operator-name,
.mq-math-mode .mq-operator-name var {
    font-family: KaTeX_Main, 'Times New Roman', serif;
    font-style: normal;
}


/* --- Icons (line drawings, no emoji!) --- */
.dl-ico { width: 20px; height: 20px; flex: none; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; vertical-align: -4px; margin-right: 6px; }
.nav-btn .dl-ico { margin-right: 0; }
.mode-card h3 { display: flex; align-items: center; gap: 8px; }
.mode-card h3 .dl-ico { margin-right: 0; }
.mode-card p { color: var(--text-muted); font-size: 0.9rem; }
.dl-lead { color: var(--text-muted); margin-bottom: 20px; }
.expr-remove-btn svg { width: 14px; height: 14px; fill: none; stroke: currentColor; stroke-width: 2.4; stroke-linecap: round; display: block; }
.expr-error { display: flex; align-items: flex-start; gap: 6px; }
.expr-error svg { width: 14px; height: 14px; flex: none; fill: none; stroke: currentColor; stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; margin-top: 1px; }
.dl-calc-card { max-width: 400px; margin: auto; }
.calc-btn.dl-eq { grid-column: span 2; }


/* --- Reordering: the grip on each function row --- */
.expr-grip { flex: none; display: grid; place-items: center; width: 16px; height: 22px; margin: 0 -2px 0 -4px; color: #b8bfca; cursor: grab; touch-action: none; user-select: none; }
.expr-grip:hover { color: var(--accent-magenta); }
.expr-grip svg { width: 16px; height: 16px; fill: none; stroke: currentColor; stroke-width: 3.2; stroke-linecap: round; }
.expr-row.dragging { opacity: 0.85; border-color: var(--accent-magenta); box-shadow: 0 6px 18px rgba(238, 0, 88, 0.3); position: relative; z-index: 3; }
.dragging-list, .dragging-list * { cursor: grabbing !important; }

/* --- The symbol keyboard --- */
.panel-title .dl-kb-toggle { margin-left: auto; display: inline-flex; align-items: center; gap: 6px; padding: 5px 12px; border-radius: 8px; border: 1px solid #fbcfe8; background: linear-gradient(180deg, #fff0f5 0%, #ffe4e9 100%); color: var(--accent-magenta); font: 700 0.72rem 'JetBrains Mono', monospace; text-transform: none; cursor: pointer; }
.panel-title .dl-kb-toggle .dl-ico { width: 16px; height: 16px; margin: 0; }
.panel-title .dl-kb-toggle:hover, .panel-title .dl-kb-toggle.active { border-color: var(--accent-magenta); background: var(--accent-magenta); color: #fff; }
.dl-kb { flex: none; margin-top: 12px; padding: 8px; border: 1px solid #f7d3e0; border-radius: 12px; background: #fff7fa; color: #1e293b; user-select: none; }
.dl-kb[hidden] { display: none; }
.dl-kb-head { display: flex; align-items: center; gap: 6px; margin-bottom: 8px; }
.dl-kb-tab { padding: 4px 12px; border-radius: 999px; border: 1px solid #fbcfe8; background: #fff; color: #64748b; font: 700 0.78rem 'JetBrains Mono', monospace; cursor: pointer; }
.dl-kb-tab.active { background: var(--accent-magenta); border-color: var(--accent-magenta); color: #fff; }
.dl-kb-hint { margin-left: auto; font-size: 0.7rem; color: #94a3b8; }
.dl-kb-close { display: grid; place-items: center; width: 24px; height: 24px; border: none; background: transparent; color: #94a3b8; cursor: pointer; border-radius: 6px; }
.dl-kb-close:hover { color: var(--accent-magenta); background: #ffe4e9; }
.dl-kb-close svg { width: 14px; height: 14px; fill: none; stroke: currentColor; stroke-width: 2.4; stroke-linecap: round; }
.dl-kb-grid { display: grid; grid-template-columns: repeat(var(--cols, 10), minmax(0, 1fr)); gap: 5px; }
.dl-key { height: 36px; min-width: 0; padding: 0 2px; border: 1px solid #f3c5d6; border-radius: 8px; background: linear-gradient(180deg, #fff 0%, #fff0f5 100%); color: #1e293b; font: 600 0.92rem KaTeX_Main, 'Times New Roman', serif; cursor: pointer; display: grid; place-items: center; box-shadow: 0 1px 0 rgba(238, 0, 88, 0.12); transition: transform 0.08s, background 0.12s; overflow: hidden; }
.dl-key:hover { border-color: var(--accent-magenta); color: var(--accent-magenta); }
.dl-key:active { transform: scale(0.94); background: #ffd6e4; }
.dl-key > svg { width: 17px; height: 17px; fill: none; stroke: currentColor; stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
.dl-key .katex { font-size: 1em; }
.dl-key-fn { font: 700 0.76rem 'JetBrains Mono', monospace; }
.dl-kb-tex .dl-key { height: 40px; font-size: 0.85rem; }