:root {
    color-scheme: light;
    --bg: #f7fbf8;
    --surface: #ffffff;
    --surface-soft: #eef8f2;
    --ink: #202824;
    --muted: #5d6a62;
    --line: #dce8e0;
    --coral: #e85d4f;
    --coral-strong: #c94439;
    --teal: #00847f;
    --teal-soft: #d9f3ed;
    --yellow: #f5c84b;
    --shadow: 0 18px 45px rgba(32, 40, 36, 0.12);
    --radius: 8px;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    min-height: 100vh;
    background:
        linear-gradient(135deg, rgba(232, 93, 79, 0.08), transparent 38%),
        linear-gradient(315deg, rgba(0, 132, 127, 0.10), transparent 42%),
        var(--bg);
    color: var(--ink);
    font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

button,
a {
    -webkit-tap-highlight-color: transparent;
}

button {
    border: 0;
    cursor: pointer;
    font: inherit;
}

button:disabled {
    cursor: not-allowed;
    opacity: 0.55;
}

.app-shell {
    width: min(1180px, calc(100% - 32px));
    margin: 0 auto;
    padding: 18px 0 40px;
}

.topbar {
    position: sticky;
    top: 0;
    z-index: 10;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    padding: 10px 0 18px;
    background: rgba(247, 251, 248, 0.88);
    backdrop-filter: blur(16px);
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    color: var(--ink);
    font-weight: 800;
    text-decoration: none;
}

.brand-mark {
    display: inline-grid;
    width: 40px;
    height: 40px;
    place-items: center;
    border-radius: var(--radius);
    background: var(--ink);
    color: #ffffff;
    font-size: 0.9rem;
}

.home-view,
.study-view {
    animation: viewIn 220ms ease-out both;
}

.is-hidden {
    display: none;
}

.intro {
    display: grid;
    grid-template-columns: minmax(0, 1.05fr) minmax(280px, 0.95fr);
    gap: 22px;
    align-items: stretch;
    min-height: 430px;
    margin-top: 8px;
}

.intro-copy {
    display: flex;
    min-width: 0;
    flex-direction: column;
    justify-content: center;
    padding: 44px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--surface);
    box-shadow: var(--shadow);
}

.eyebrow {
    margin: 0 0 10px;
    color: var(--teal);
    font-size: 0.78rem;
    font-weight: 800;
    letter-spacing: 0;
    text-transform: uppercase;
}

h1,
h2,
h3,
p {
    overflow-wrap: anywhere;
}

h1,
h2,
h3 {
    margin: 0;
    line-height: 1.08;
}

h1 {
    max-width: 760px;
    font-size: 3rem;
}

h2 {
    font-size: 1.85rem;
}

h3 {
    font-size: 1.12rem;
}

.intro-text,
.study-panel p,
.module-card p {
    color: var(--muted);
    line-height: 1.65;
}

.intro-text {
    max-width: 660px;
    margin: 20px 0 0;
    font-size: 1.06rem;
}

.intro-visual {
    position: relative;
    min-height: 360px;
    margin: 0;
    overflow: hidden;
    border-radius: var(--radius);
    background: var(--surface-soft);
    box-shadow: var(--shadow);
}

.intro-visual::after {
    content: "";
    position: absolute;
    inset: 0;
    background: linear-gradient(180deg, transparent 20%, rgba(32, 40, 36, 0.22));
}

.intro-visual img {
    width: 100%;
    height: 100%;
    display: block;
    object-fit: cover;
    object-position: center right;
}

.global-progress {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 12px;
    margin: 18px 0 34px;
}

.global-progress > div,
.study-panel,
.module-card {
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: rgba(255, 255, 255, 0.94);
}

.global-progress > div {
    padding: 20px;
}

.stat-number,
.stat-label {
    display: block;
}

.stat-number {
    font-size: 2rem;
    font-weight: 900;
    color: var(--coral-strong);
}

.stat-label {
    margin-top: 4px;
    color: var(--muted);
}

.section-heading {
    display: flex;
    align-items: end;
    justify-content: space-between;
    gap: 20px;
    margin-bottom: 14px;
}

.module-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 14px;
}

.module-card {
    display: flex;
    min-height: 230px;
    flex-direction: column;
    justify-content: space-between;
    gap: 20px;
    padding: 22px;
    text-align: left;
    transition: transform 160ms ease, border-color 160ms ease, box-shadow 160ms ease;
}

.module-card:hover,
.module-card:focus-visible {
    border-color: rgba(0, 132, 127, 0.7);
    box-shadow: 0 14px 30px rgba(32, 40, 36, 0.12);
    outline: none;
    transform: translateY(-2px);
}

.module-card.is-empty {
    background: rgba(238, 248, 242, 0.74);
}

.module-kicker,
.card-label {
    color: var(--coral-strong);
    font-size: 0.78rem;
    font-weight: 900;
    letter-spacing: 0;
    text-transform: uppercase;
}

.module-card p {
    margin: 12px 0 0;
}

.module-meta {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 10px;
    color: var(--muted);
    font-size: 0.92rem;
}

.mini-track {
    position: relative;
    width: 82px;
    height: 8px;
    overflow: hidden;
    border-radius: var(--radius);
    background: #e9efe9;
}

.mini-track span {
    position: absolute;
    inset: 0 auto 0 0;
    width: var(--progress, 0%);
    border-radius: inherit;
    background: var(--teal);
}

.back-button {
    display: inline-flex;
    align-items: center;
    min-height: 44px;
    margin: 6px 0 18px;
    padding: 0 16px;
    border-radius: var(--radius);
    background: var(--surface);
    color: var(--ink);
    font-weight: 800;
    box-shadow: inset 0 0 0 1px var(--line);
}

.study-layout {
    display: grid;
    grid-template-columns: minmax(250px, 0.82fr) minmax(0, 1.18fr);
    gap: 20px;
    align-items: start;
}

.study-panel {
    position: sticky;
    top: 78px;
    padding: 24px;
    box-shadow: var(--shadow);
}

.study-panel h1 {
    font-size: 2rem;
}

.module-intro {
    display: grid;
    gap: 12px;
    margin-top: 20px;
}

.intro-block {
    padding: 14px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--surface-soft);
}

.intro-block h2 {
    margin-bottom: 8px;
    font-size: 1rem;
}

.intro-block p {
    margin: 0;
}

.checklist {
    display: grid;
    gap: 10px;
    margin: 0;
    padding: 0;
    list-style: none;
}

.checklist li {
    color: var(--muted);
    line-height: 1.45;
}

.checklist label {
    display: grid;
    grid-template-columns: 22px minmax(0, 1fr);
    gap: 10px;
    align-items: start;
    cursor: pointer;
}

.checklist input {
    width: 20px;
    height: 20px;
    margin: 1px 0 0;
    accent-color: var(--teal);
}

.checklist input:focus-visible {
    outline: 3px solid rgba(0, 132, 127, 0.28);
    outline-offset: 2px;
}

.checklist input:checked + span {
    color: var(--ink);
    font-weight: 750;
}

.meter {
    margin-top: 28px;
}

.meter-info {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    color: var(--muted);
    font-size: 0.92rem;
}

.meter-track {
    position: relative;
    height: 12px;
    margin-top: 10px;
    overflow: hidden;
    border-radius: var(--radius);
    background: #e9efe9;
}

.meter-track span {
    position: absolute;
    inset: 0 auto 0 0;
    width: 0;
    border-radius: inherit;
    background: linear-gradient(90deg, var(--teal), var(--yellow));
    transition: width 180ms ease;
}

.study-tools,
.practice-actions,
.navigation-actions {
    display: flex;
    gap: 10px;
}

.study-tools {
    flex-wrap: wrap;
    margin-top: 24px;
}

.card-zone {
    display: grid;
    gap: 14px;
}

.flashcard {
    height: clamp(440px, 58vh, 620px);
    min-height: 440px;
    perspective: 1200px;
    outline: none;
}

.flashcard:focus-visible .flashcard-inner {
    box-shadow: 0 0 0 4px rgba(0, 132, 127, 0.22), var(--shadow);
}

.flashcard-inner {
    position: relative;
    width: 100%;
    min-height: inherit;
    transform-style: preserve-3d;
    transition: transform 260ms ease;
}

.flashcard.is-flipped .flashcard-inner {
    transform: rotateY(180deg);
}

.flashcard-face {
    position: absolute;
    inset: 0;
    display: flex;
    min-width: 0;
    flex-direction: column;
    justify-content: center;
    gap: 24px;
    padding: 38px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--surface);
    box-shadow: var(--shadow);
    backface-visibility: hidden;
    overflow-y: auto;
}

.flashcard-front {
    border-top: 8px solid var(--coral);
}

.flashcard-back {
    border-top: 8px solid var(--teal);
    background: #fbfefc;
    transform: rotateY(180deg);
}

.flashcard h2 {
    font-size: 2.1rem;
}

.flashcard-back p:not(.card-label) {
    margin: 0;
    color: var(--ink);
    font-size: 1.22rem;
    line-height: 1.7;
}

.tap-hint {
    align-self: flex-start;
    padding: 8px 10px;
    border-radius: var(--radius);
    background: var(--teal-soft);
    color: #0f625f;
    font-size: 0.92rem;
    font-weight: 800;
}

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

.navigation-actions {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
}

.primary-button,
.secondary-button,
.ghost-button {
    min-height: 46px;
    padding: 0 16px;
    border-radius: var(--radius);
    font-weight: 850;
}

.primary-button {
    background: var(--coral);
    color: #ffffff;
}

.primary-button:hover,
.primary-button:focus-visible {
    background: var(--coral-strong);
}

.secondary-button {
    background: var(--teal);
    color: #ffffff;
}

.secondary-button:hover,
.secondary-button:focus-visible {
    background: #006f6b;
}

.ghost-button {
    background: var(--surface);
    color: var(--ink);
    box-shadow: inset 0 0 0 1px var(--line);
}

.ghost-button:hover,
.ghost-button:focus-visible,
.back-button:hover,
.back-button:focus-visible {
    box-shadow: inset 0 0 0 2px var(--teal);
    outline: none;
}

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

@media (max-width: 920px) {
    .intro,
    .study-layout {
        grid-template-columns: 1fr;
    }

    .intro {
        min-height: 0;
    }

    .intro-visual {
        min-height: 260px;
        order: -1;
    }

    .module-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .study-panel {
        position: static;
    }
}

@media (max-width: 640px) {
    .app-shell {
        width: min(100% - 22px, 1180px);
        padding-bottom: 24px;
    }

    .topbar {
        padding-bottom: 12px;
    }

    .brand span:last-child {
        display: none;
    }

    .intro-copy,
    .study-panel,
    .flashcard-face,
    .module-card,
    .global-progress > div {
        padding: 18px;
    }

    h1 {
        font-size: 2.08rem;
    }

    h2,
    .flashcard h2 {
        font-size: 1.48rem;
    }

    .study-panel h1 {
        font-size: 1.75rem;
    }

    .global-progress,
    .module-grid {
        grid-template-columns: 1fr;
    }

    .global-progress {
        margin-bottom: 26px;
    }

    .module-card {
        min-height: 190px;
    }

    .flashcard {
        height: 430px;
        min-height: 390px;
    }

    .flashcard-back p:not(.card-label) {
        font-size: 1rem;
        line-height: 1.58;
    }

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

    .practice-actions {
        position: sticky;
        bottom: 10px;
        z-index: 5;
        padding: 8px;
        border: 1px solid var(--line);
        border-radius: var(--radius);
        background: rgba(255, 255, 255, 0.94);
        backdrop-filter: blur(12px);
    }
}

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 1ms !important;
        scroll-behavior: auto !important;
        transition-duration: 1ms !important;
    }
}