/* ===============================
   NeetCode 150 — Fluent Light Edition
   Microsoft 365 brand accents, light-first, accessible
   =============================== */

/* Brand tokens (Microsoft logo + Office orange) */
:root {
    --ms-blue: #00A4EF;
    /* Microsoft Blue */
    /* source: color palette */
    --ms-green: #7FBA00;
    /* Microsoft Green */
    --ms-red: #F25022;
    /* Microsoft Orange-Red */
    --ms-yellow: #FFB900;
    /* Microsoft Yellow */
    --ms-office: #D83B01;
    /* Office orange */

    /* Primitives */
    --bg: #f7f9fc;
    --bg-2: #ffffff;
    --text: #0f172a;
    /* slate-900 */
    --muted: #64748b;
    /* slate-500 */
    --line: rgba(2, 6, 23, .08);

    --radius: 14px;
    --radius-sm: 10px;
    --shadow-1: 0 1px 2px rgba(2, 6, 23, .04), 0 8px 24px rgba(2, 6, 23, .08);
    --shadow-2: 0 8px 30px rgba(2, 6, 23, .10);

    /* Primary accent (used for CTAs/focus) - Blue */
    --accent: var(--ms-blue);
    --accent-2: #4cc9ff;
    /* light blue for gradients */

    /* Difficulty colors */
    --easy: #16a34a;
    /* green-600 */
    --medium: #ea580c;
    /* orange-600 */
    --hard: #6366f1;
    /* indigo-500 */
}

/* Support dark mode preference gracefully */
@media (prefers-color-scheme: dark) {
    :root {
        --bg: #0b1220;
        --bg-2: #101826;
        --text: #e5e7eb;
        --muted: #9aa5b1;
        --line: rgba(255, 255, 255, .08);
        --shadow-1: 0 1px 2px rgba(0, 0, 0, .2), 0 8px 24px rgba(0, 0, 0, .3);
        --shadow-2: 0 8px 30px rgba(0, 0, 0, .45);
    }
}

/* Global reset */
* {
    box-sizing: border-box
}

html,
body {
    height: 100%
}

body {
    margin: 0;
    font: 14px/1.55 system-ui, -apple-system, Segoe UI, Roboto, Inter, Arial, sans-serif;
    color: var(--text);
    background: var(--bg);
}

/* Background decor: subtle grid + soft spots in MS colors */
.bg-stage {
    position: fixed;
    inset: 0;
    z-index: 0;
    pointer-events: none;
}

.bg-grid {
    position: absolute;
    inset: 0;
    background-image:
        linear-gradient(to right, rgba(2, 6, 23, 0.04) 1px, transparent 1px),
        linear-gradient(to bottom, rgba(2, 6, 23, 0.04) 1px, transparent 1px);
    background-size: 24px 24px;
    mask-image: radial-gradient(1200px 600px at 50% -10%, #000 0, #000 40%, transparent 70%);
}

.bg-spot {
    position: absolute;
    width: 50vmax;
    height: 50vmax;
    filter: blur(80px);
    opacity: .25;
    border-radius: 999px;
}

.bg-spot.b-blue {
    left: -20vmax;
    top: -10vmax;
    background: var(--ms-blue);
}

.bg-spot.b-orange {
    right: -15vmax;
    top: 20vh;
    background: var(--ms-red);
}

.bg-spot.b-green {
    right: -25vmax;
    bottom: -10vmax;
    background: var(--ms-green);
}

.bg-noise {
    position: absolute;
    inset: 0;
    opacity: .04;
    mix-blend-mode: multiply;
    background-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="140" height="140" viewBox="0 0 140 140"><filter id="n"><feTurbulence baseFrequency=".8" numOctaves="2" seed="7" type="fractalNoise"/></filter><rect width="100%" height="100%" filter="url(%23n)"/></svg>');
}

/* App shell */
.app-shell {
    position: relative;
    z-index: 1;
    max-width: 1200px;
    padding: 28px;
    margin-inline: auto;
}

/* Cards */
.card {
    background: var(--bg-2);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    box-shadow: var(--shadow-1);
}

/* Header */
.app-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    padding: 16px 18px;
    margin-bottom: 16px;
    background: var(--bg-2);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    box-shadow: var(--shadow-1);
}

.title {
    display: flex;
    align-items: center;
    gap: 14px;
}

.ms-mark {
    width: 32px;
    height: 32px;
}

h1 {
    font-size: 20px;
    margin: 0;
    letter-spacing: .2px;
}

.subtitle {
    margin: 2px 0 0;
    color: var(--muted);
    font-size: 12px;
}

/* Tabs */
.tabs {
    display: flex;
    gap: 8px;
    padding: 4px;
    border-radius: 999px;
    background: rgba(2, 6, 23, .04);
}

.tab {
    appearance: none;
    border: 0;
    cursor: pointer;
    padding: 8px 14px;
    border-radius: 999px;
    background: transparent;
    color: var(--text);
    font-weight: 600;
    transition: all .2s ease;
}

.tab:hover {
    background: rgba(2, 6, 23, .06);
}

.tab.active {
    color: #fff;
    background:
        linear-gradient(90deg, var(--ms-blue), var(--ms-green), var(--ms-yellow), var(--ms-red));
    background-size: 200% 100%;
    animation: slide-grad 6s linear infinite;
    box-shadow: 0 8px 18px rgba(0, 164, 239, .25);
}

@keyframes slide-grad {
    to {
        background-position: 200% 0;
    }
}

/* Toolbar */
.toolbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    padding: 14px 16px;
    margin: 16px 0;
}

.points .label {
    color: var(--muted);
    font-weight: 600;
}

.points .value {
    font-weight: 700;
    font-size: 24px;
    padding-left: 10px;
    background: linear-gradient(90deg, var(--ms-blue), var(--ms-green));
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}

/* Buttons — keep classes & names */
button {
    appearance: none;
    cursor: pointer;
    border-radius: 12px;
    padding: 10px 14px;
    border: 1px solid rgba(2, 6, 23, .08);
    background: #fff;
    color: var(--text);
    font-weight: 600;
    letter-spacing: .2px;
    transition: transform .12s ease, box-shadow .2s ease, background .2s ease, border-color .2s ease;
}

button:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-1);
}

button.secondary {
    background: linear-gradient(to bottom right, #fff, #f3f7fb);
}

button.danger {
    color: #fff;
    background: var(--ms-red);
    border-color: rgba(242, 80, 34, .8);
    box-shadow: 0 8px 18px rgba(242, 80, 34, .2);
}

button.primary {
    color: #fff;
    background: linear-gradient(90deg, var(--accent), var(--accent-2));
    border-color: rgba(0, 164, 239, .6);
    box-shadow: 0 10px 24px rgba(0, 164, 239, .25);
}

/* Filters */
.filters {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    padding: 14px 16px;
    margin-bottom: 16px;
}

.field {
    display: flex;
    flex-direction: column;
    gap: 6px;
    min-width: 180px;
}

.field span {
    font-size: 12px;
    color: var(--muted);
    font-weight: 600;
}

.filters input,
.filters select {
    padding: 10px 12px;
    border: 1px solid var(--line);
    border-radius: 12px;
    background: #fff;
    outline: none;
    color: var(--text);
    font-weight: 500;
    transition: box-shadow .2s ease, border-color .2s ease;
}

.filters input:focus,
.filters select:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(0, 164, 239, .2);
}

/* Accordion sections */
.accordion {
    display: grid;
    gap: 12px;
}

.section {
    overflow: hidden;
    border-radius: var(--radius);
    border: 1px solid var(--line);
    background: var(--bg-2);
    box-shadow: var(--shadow-1);
}

.section summary {
    list-style: none;
    cursor: pointer;
    padding: 14px 16px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.section summary::-webkit-details-marker {
    display: none;
}

.section h3 {
    margin: 0;
    font-size: 16px;
}

.section .sub {
    color: var(--muted);
    font-size: 12px;
    margin-left: 8px;
}

/* Progress */
.progress {
    display: flex;
    align-items: center;
    gap: 10px;
    min-width: 200px;
}

.progress .bar {
    flex: 1;
    height: 10px;
    border-radius: 999px;
    background: rgba(2, 6, 23, .08);
    overflow: hidden;
    border: 1px solid var(--line);
}

.progress .bar span {
    display: block;
    height: 100%;
    background: linear-gradient(90deg, var(--ms-blue), var(--ms-green), var(--ms-yellow));
    width: 0%;
}

.progress .meta {
    color: var(--muted);
    font-size: 12px;
}

.progress-lg .bar {
    height: 12px;
}

/* Problem rows (inside details list) */
.list {
    margin: 0;
}

.problem {
    display: grid;
    grid-template-columns: 28px 1fr auto auto auto;
    gap: 10px;
    align-items: center;
    padding: 12px 16px;
    border-top: 1px solid var(--line);
    transition: background .2s ease;
}

.problem:hover {
    background: rgba(2, 6, 23, .03);
}

.title-cell {
    font-weight: 600;
}

/* Badges */
.badge {
    font-size: 12px;
    padding: 4px 10px;
    border-radius: 999px;
    background: #f3f7fb;
    color: #0f172a;
    border: 1px solid var(--line);
    font-weight: 600;
}

.badge.easy {
    background: rgba(22, 163, 74, .12);
    color: #065f46;
    border-color: rgba(22, 163, 74, .25);
}

.badge.medium {
    background: rgba(234, 88, 12, .12);
    color: #7c2d12;
    border-color: rgba(234, 88, 12, .25);
}

.badge.hard {
    background: rgba(99, 102, 241, .12);
    color: #3730a3;
    border-color: rgba(99, 102, 241, .25);
}

.badge.topic {
    background: rgba(0, 164, 239, .08);
    color: #0b5394;
    border-color: rgba(0, 164, 239, .25);
}

/* All Problems table */
.table-wrap {
    overflow: auto;
}

.problems-table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
}

.problems-table thead th {
    position: sticky;
    top: 0;
    background: #fff;
    border-bottom: 1px solid var(--line);
    box-shadow: 0 2px 0 rgba(2, 6, 23, .02);
}

.problems-table th,
.problems-table td {
    padding: 12px 14px;
    border-bottom: 1px solid var(--line);
}

.problems-table tbody tr:hover {
    background: rgba(2, 6, 23, .03);
}

/* Stats */
.stats-grid {
    display: grid;
    gap: 12px;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.card {
    padding: 16px;
}

.list ul,
.list li {
    list-style: none;
    padding: 0;
    margin: 0;
}

.list li {
    padding: 10px 0;
    border-bottom: 1px solid var(--line);
    display: flex;
    align-items: center;
    gap: 8px;
    justify-content: space-between;
}

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

.dot.easy {
    background: var(--easy);
}

.dot.medium {
    background: var(--medium);
}

.dot.hard {
    background: var(--hard);
}

/* Footer */
.app-footer {
    margin-top: 20px;
    padding: 14px 16px;
    color: var(--muted);
    text-align: center;
    background: var(--bg-2);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    box-shadow: var(--shadow-1);
}

/* Checkbox */
.checkbox {
    appearance: none;
    inline-size: 20px;
    block-size: 20px;
    border-radius: 6px;
    border: 1px solid rgba(2, 6, 23, .2);
    background: #fff;
    display: grid;
    place-items: center;
    cursor: pointer;
    transition: all .15s ease;
}

.checkbox:hover {
    border-color: var(--accent);
}

.checkbox:checked {
    background: linear-gradient(135deg, var(--accent), var(--accent-2));
    border-color: rgba(0, 164, 239, .9);
    box-shadow: 0 6px 14px rgba(0, 164, 239, .25);
}

.checkbox:checked::after {
    content: "";
    width: 10px;
    height: 10px;
    transform: rotate(45deg);
    border-right: 2px solid #fff;
    border-bottom: 2px solid #fff;
    margin-top: -2px;
}

/* Focus rings */
:focus-visible {
    outline: none;
    box-shadow: 0 0 0 3px rgba(0, 164, 239, .35) !important;
    border-color: var(--accent) !important;
}

/* Responsive tweaks */
@media (max-width: 640px) {
    .app-shell {
        padding: 18px;
    }

    .progress {
        min-width: 140px;
    }

    .problem {
        grid-template-columns: 24px 1fr auto;
    }

    .problem span.badge:nth-of-type(2),
    /* topic */
    .problem span.points {
        display: none;
    }

    /* points */
}