:root {
    --study-blue: #2f7cf6;
    --study-red: #ef4d43;
    --study-yellow: #f6b91f;
    --study-green: #45ae55;
    --ink: #111111;
    --muted: #6d6d72;
    --line: #e4e5e8;
    --panel: #f5f6f8;
    --max-width: 1120px;
}

button,
input {
    font: inherit;
}

.study-main {
    width: 100%;
    overflow: hidden;
    color: var(--ink);
}

.study-intro,
.category-section,
.deck-section {
    width: min(100%, var(--max-width));
    margin: 0 auto;
    padding: 38px 20px;
}

.study-intro {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 230px;
    gap: 40px;
    align-items: end;
    padding-top: 52px;
    padding-bottom: 44px;
}

.study-kicker,
.step-label,
.example-label {
    margin: 0 0 8px;
    color: var(--study-blue);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.82rem;
    font-weight: 700;
    text-transform: uppercase;
}

.study-app-link {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 18px;
    border-radius: 8px;
    color: inherit;
    text-decoration: none;
}

.study-app-link img {
    width: 56px;
    height: 56px;
    border-radius: 14px;
    transition: transform 0.18s ease;
}

.study-app-link .study-kicker {
    margin: 0;
}

.study-app-link:hover img {
    transform: translateY(-2px);
}

.study-app-link:hover .study-kicker {
    color: var(--ink);
}

.study-app-link:focus-visible {
    outline: 3px solid var(--ink);
    outline-offset: 4px;
}

.study-intro h1 {
    margin: 0;
    font-family: Helvetica, Arial, sans-serif;
    font-size: clamp(2.5rem, 7vw, 5.4rem);
    line-height: 0.98;
    letter-spacing: 0;
}

.study-lead {
    max-width: 760px;
    margin: 20px 0 0;
    color: var(--muted);
    font-family: Helvetica, Arial, sans-serif;
    font-size: clamp(1.02rem, 2vw, 1.25rem);
    line-height: 1.55;
}

.study-summary {
    padding: 20px 0 4px 24px;
    border-left: 1px solid var(--line);
}

.study-summary strong {
    display: block;
    font-family: Helvetica, Arial, sans-serif;
    font-size: 2.7rem;
    line-height: 1;
}

.study-summary span {
    display: block;
    margin-top: 8px;
    color: var(--muted);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.95rem;
    line-height: 1.4;
}

.study-summary .study-version {
    width: fit-content;
    margin-top: 12px;
    padding: 4px 7px;
    border: 1px solid var(--line);
    border-radius: 4px;
    color: var(--ink);
    font-size: 0.72rem;
    font-weight: 700;
}

.study-mode-switch {
    display: grid;
    width: min(calc(100% - 40px), var(--max-width));
    grid-template-columns: repeat(4, minmax(0, 1fr));
    margin: 0 auto 38px;
    padding: 4px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--panel);
}

.study-mode-switch a {
    display: flex;
    min-height: 44px;
    align-items: center;
    justify-content: center;
    padding: 8px 14px;
    border-radius: 6px;
    color: var(--muted);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.94rem;
    font-weight: 700;
    text-align: center;
    text-decoration: none;
}

.study-mode-switch a:hover {
    color: var(--ink);
}

.study-mode-switch a[aria-current="page"] {
    background: #ffffff;
    color: var(--ink);
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.1);
}

.study-mode-switch a:focus-visible {
    outline: 3px solid var(--ink);
    outline-offset: 2px;
}

.vocabulary-view-switch {
    display: grid;
    width: min(calc(100% - 40px), var(--max-width));
    grid-template-columns: repeat(2, minmax(0, 1fr));
    margin: 0 auto 38px;
    padding: 4px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--panel);
}

.vocabulary-view-switch button {
    min-height: 44px;
    padding: 8px 14px;
    border: 0;
    border-radius: 6px;
    background: transparent;
    color: var(--muted);
    cursor: pointer;
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.94rem;
    font-weight: 700;
    appearance: none;
}

.vocabulary-view-switch button:hover {
    color: var(--ink);
}

.vocabulary-view-switch button[aria-pressed="true"] {
    background: #ffffff;
    color: var(--ink);
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.1);
}

.vocabulary-view-switch button:focus-visible {
    outline: 3px solid var(--ink);
    outline-offset: 2px;
}

.category-section {
    width: 100%;
    max-width: none;
    padding-left: max(20px, calc((100% - var(--max-width)) / 2 + 20px));
    padding-right: max(20px, calc((100% - var(--max-width)) / 2 + 20px));
    background: var(--panel);
    border-top: 1px solid var(--line);
    border-bottom: 1px solid var(--line);
}

.section-title-row {
    display: flex;
    align-items: end;
    justify-content: space-between;
    gap: 20px;
    margin-bottom: 22px;
}

.section-title-row h2 {
    margin: 0;
    font-family: Helvetica, Arial, sans-serif;
    font-size: clamp(1.65rem, 3.6vw, 2.45rem);
    letter-spacing: 0;
}

.category-count,
.deck-description {
    margin: 8px 0 0;
    color: var(--muted);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.96rem;
    line-height: 1.45;
}

.category-list {
    display: grid;
    grid-template-columns: repeat(5, minmax(0, 1fr));
    gap: 10px;
}

.category-button {
    --category-colour: var(--study-blue);
    position: relative;
    min-height: 94px;
    padding: 16px;
    overflow: hidden;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #ffffff;
    color: var(--ink);
    cursor: pointer;
    text-align: left;
    appearance: none;
    transition: border-color 0.18s ease, box-shadow 0.18s ease, transform 0.18s ease;
}

.category-button::before {
    content: "";
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    width: 5px;
    background: var(--category-colour);
}

.category-button:hover {
    border-color: #b9bbc0;
    transform: translateY(-2px);
}

.category-button[aria-pressed="true"] {
    border-color: var(--category-colour);
    box-shadow: inset 0 0 0 1px var(--category-colour);
}

.category-button strong,
.category-button span {
    display: block;
    font-family: Helvetica, Arial, sans-serif;
}

.category-button strong {
    padding-right: 8px;
    font-size: 0.98rem;
    line-height: 1.25;
}

.category-button span {
    margin-top: 8px;
    color: var(--muted);
    font-size: 0.8rem;
}

.deck-section {
    padding-top: 46px;
    padding-bottom: 54px;
}

.deck-heading-row {
    align-items: center;
}

.deck-progress {
    flex: 0 0 auto;
    min-width: 126px;
    padding: 12px 14px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #ffffff;
    text-align: center;
}

.deck-progress strong,
.deck-progress span {
    display: block;
    font-family: Helvetica, Arial, sans-serif;
}

.deck-progress strong {
    font-size: 1.5rem;
}

.deck-progress span {
    margin-top: 3px;
    color: var(--muted);
    font-size: 0.76rem;
}

.card-grid {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 12px;
}

.vocab-card {
    --card-colour: var(--study-blue);
    position: relative;
    display: flex;
    min-width: 0;
    min-height: 190px;
    align-items: stretch;
    padding: 0;
    border: 0;
    border-radius: 8px;
    background: transparent;
    color: var(--ink);
    cursor: pointer;
    appearance: none;
    perspective: 900px;
}

.card-inner {
    position: relative;
    width: 100%;
    min-height: 190px;
    transform-style: preserve-3d;
    transition: transform 0.42s ease;
}

.vocab-card.is-revealed .card-inner {
    transform: rotateY(180deg);
}

.card-face {
    position: absolute;
    inset: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-width: 0;
    padding: 18px 12px;
    border: 1px solid var(--line);
    border-radius: 8px;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.07);
}

.card-front {
    background: linear-gradient(160deg, #ffffff 54%, color-mix(in srgb, var(--card-colour) 14%, white));
}

.vocab-card.is-seen .card-front {
    border-color: color-mix(in srgb, var(--card-colour) 48%, white);
    background: color-mix(in srgb, var(--card-colour) 17%, white);
}

.seen-marker {
    position: absolute;
    top: 10px;
    right: 10px;
    display: none;
    width: 23px;
    height: 23px;
    place-items: center;
    border: 1px solid color-mix(in srgb, var(--card-colour) 66%, #111111);
    border-radius: 50%;
    background: color-mix(in srgb, var(--card-colour) 34%, white);
    color: var(--ink);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.78rem;
    font-weight: 700;
    line-height: 1;
}

.vocab-card.is-seen .seen-marker {
    display: grid;
}

.card-back {
    border-color: var(--card-colour);
    background: var(--card-colour);
    color: #ffffff;
    transform: rotateY(180deg);
}

.is-kanji-view .card-back {
    background: color-mix(in srgb, var(--card-colour) 60%, #000000);
}

.kanji-card-example {
    max-width: 100%;
    margin-top: 12px;
    font-family: "Hiragino Sans", "Yu Gothic", "Noto Sans JP", sans-serif;
    font-size: 0.88rem;
    line-height: 1.4;
    overflow-wrap: anywhere;
}

.script-label {
    position: absolute;
    top: 12px;
    left: 12px;
    color: var(--muted);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.69rem;
    font-weight: 700;
    text-transform: uppercase;
}

.japanese-word {
    max-width: 100%;
    font-family: "Hiragino Sans", "Yu Gothic", "Noto Sans JP", sans-serif;
    font-size: clamp(1.65rem, 3vw, 2.35rem);
    font-weight: 600;
    line-height: 1.3;
    overflow-wrap: anywhere;
}

.is-kanji-view .japanese-word {
    font-size: 3.5rem;
    line-height: 1;
}

ruby {
    ruby-position: over;
}

rt {
    font-family: "Hiragino Sans", "Yu Gothic", "Noto Sans JP", sans-serif;
    font-size: 0.42em;
    font-weight: 500;
}

.tap-hint {
    position: absolute;
    right: 12px;
    bottom: 11px;
    color: var(--muted);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.67rem;
}

.card-back .tap-hint {
    color: rgba(255, 255, 255, 0.82);
}

.english-word {
    max-width: 100%;
    font-family: Helvetica, Arial, sans-serif;
    font-size: clamp(1.1rem, 2vw, 1.45rem);
    font-weight: 700;
    line-height: 1.25;
    overflow-wrap: anywhere;
}

.pair-label {
    margin-top: 10px;
    color: rgba(255, 255, 255, 0.78);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.74rem;
    line-height: 1.3;
}

.vocab-card:focus-visible,
.category-button:focus-visible {
    outline: 3px solid var(--ink);
    outline-offset: 3px;
}

.example-panel,
.example-placeholder {
    min-height: 138px;
    margin-top: 26px;
    border-top: 1px solid var(--line);
}

.example-panel {
    display: grid;
    grid-template-columns: 76px minmax(0, 1fr);
    gap: 20px;
    align-items: center;
    padding-top: 26px;
}

.example-panel[hidden] {
    display: none;
}

.example-placeholder[hidden] {
    display: none;
}

.example-marker,
.example-placeholder span {
    display: grid;
    width: 64px;
    height: 64px;
    place-items: center;
    border-radius: 8px;
    background: var(--study-red);
    color: #ffffff;
    font-family: "Hiragino Sans", "Yu Gothic", sans-serif;
    font-size: 2rem;
}

.example-japanese {
    margin: 0;
    font-family: "Hiragino Sans", "Yu Gothic", "Noto Sans JP", sans-serif;
    font-size: clamp(1.25rem, 3vw, 1.8rem);
    line-height: 1.65;
}

.example-english {
    margin: 7px 0 0;
    color: var(--muted);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.98rem;
    line-height: 1.45;
}

.example-placeholder {
    display: flex;
    align-items: center;
    gap: 18px;
    padding-top: 26px;
    color: var(--muted);
}

.example-placeholder span {
    flex: 0 0 52px;
    width: 52px;
    height: 52px;
    background: #d8d9dc;
    font-size: 1.55rem;
}

.example-placeholder p {
    margin: 0;
    font-family: Helvetica, Arial, sans-serif;
    line-height: 1.5;
}

.sentence-heading-row {
    align-items: center;
}

.sentence-actions {
    display: flex;
    flex: 0 0 auto;
    align-items: center;
    gap: 8px;
}

.study-control {
    min-height: 44px;
    padding: 9px 14px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #ffffff;
    color: var(--ink);
    cursor: pointer;
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.86rem;
    font-weight: 700;
    appearance: none;
    transition: border-color 0.18s ease, background-color 0.18s ease;
}

.study-control:hover {
    border-color: #a9abb0;
    background: var(--panel);
}

.study-control:focus-visible {
    outline: 3px solid var(--ink);
    outline-offset: 3px;
}

.answer-note {
    margin: -4px 0 20px;
    padding: 12px 14px;
    border-left: 4px solid var(--study-yellow);
    background: #fff9e8;
    color: #55514a;
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.88rem;
    line-height: 1.45;
}

.sentence-list {
    display: grid;
    gap: 12px;
}

.sentence-card {
    --sentence-colour: var(--study-blue);
    position: relative;
    display: block;
    width: 100%;
    min-width: 0;
    padding: 0;
    overflow: hidden;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #ffffff;
    color: var(--ink);
    cursor: pointer;
    text-align: left;
    appearance: none;
    transition: border-color 0.18s ease, box-shadow 0.18s ease, transform 0.18s ease;
}

.sentence-card::before {
    content: "";
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    width: 5px;
    background: var(--sentence-colour);
}

.sentence-card:hover {
    border-color: #b9bbc0;
    transform: translateY(-1px);
}

.sentence-card.is-revealed {
    border-color: var(--sentence-colour);
    box-shadow: inset 0 0 0 1px var(--sentence-colour);
}

.sentence-card:focus-visible {
    outline: 3px solid var(--ink);
    outline-offset: 3px;
}

.sentence-prompt {
    display: grid;
    grid-template-columns: 36px minmax(0, 1fr) auto;
    gap: 14px;
    align-items: center;
    min-height: 76px;
    padding: 17px 18px 17px 20px;
}

.sentence-number {
    display: grid;
    width: 32px;
    height: 32px;
    place-items: center;
    border-radius: 50%;
    background: color-mix(in srgb, var(--sentence-colour) 14%, white);
    color: var(--ink);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.78rem;
    font-weight: 700;
}

.sentence-english {
    min-width: 0;
    font-family: Helvetica, Arial, sans-serif;
    font-size: clamp(1rem, 2vw, 1.18rem);
    font-weight: 700;
    line-height: 1.4;
    overflow-wrap: anywhere;
}

.sentence-hint {
    color: var(--muted);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.72rem;
    white-space: nowrap;
}

.sentence-answer {
    display: block;
    margin: 0 18px 0 70px;
    padding: 18px 0 20px;
    border-top: 1px solid var(--line);
}

.sentence-answer[hidden] {
    display: none;
}

.sentence-japanese {
    display: block;
    font-family: "Hiragino Sans", "Yu Gothic", "Noto Sans JP", sans-serif;
    font-size: clamp(1.22rem, 3vw, 1.75rem);
    font-weight: 600;
    line-height: 1.8;
}

.sentence-pattern {
    display: block;
    margin-top: 9px;
    color: var(--muted);
    font-family: Helvetica, Arial, sans-serif;
    font-size: 0.82rem;
    line-height: 1.45;
}

.sentence-pattern strong {
    color: var(--ink);
}

@media (max-width: 900px) {
    .category-list {
        grid-template-columns: repeat(3, minmax(0, 1fr));
    }

    .card-grid {
        grid-template-columns: repeat(3, minmax(0, 1fr));
    }
}

@media (max-width: 640px) {
    .study-mode-switch {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .study-intro {
        grid-template-columns: 1fr;
        gap: 24px;
        padding-top: 34px;
        padding-bottom: 32px;
    }

    .study-summary {
        display: flex;
        align-items: baseline;
        gap: 10px;
        padding: 16px 0 0;
        border-top: 1px solid var(--line);
        border-left: 0;
    }

    .study-summary strong {
        font-size: 2rem;
    }

    .study-summary span {
        margin: 0;
    }

    .study-summary .study-version {
        margin-left: auto;
    }

    .study-app-link img {
        width: 50px;
        height: 50px;
        border-radius: 12px;
    }

    .section-title-row {
        align-items: flex-start;
    }

    .category-count {
        display: none;
    }

    .category-list {
        display: flex;
        width: calc(100% + 20px);
        gap: 10px;
        padding-right: 20px;
        overflow-x: auto;
        overscroll-behavior-inline: contain;
        scroll-snap-type: inline proximity;
        scrollbar-width: none;
    }

    .category-list::-webkit-scrollbar {
        display: none;
    }

    .category-button {
        flex: 0 0 154px;
        scroll-snap-align: start;
    }

    .deck-heading-row {
        align-items: center;
    }

    .deck-progress {
        min-width: 108px;
    }

    .card-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
        gap: 10px;
    }

    .vocab-card,
    .card-inner {
        min-height: 164px;
    }

    .example-panel {
        grid-template-columns: 52px minmax(0, 1fr);
        gap: 14px;
        align-items: start;
    }

    .example-marker {
        width: 52px;
        height: 52px;
        font-size: 1.55rem;
    }

    .sentence-heading-row {
        display: block;
    }

    .sentence-actions {
        margin-top: 18px;
    }

    .sentence-actions .deck-progress {
        margin-left: auto;
    }

    .sentence-prompt {
        grid-template-columns: 32px minmax(0, 1fr);
        gap: 11px;
        padding: 15px 14px 15px 18px;
    }

    .sentence-number {
        width: 30px;
        height: 30px;
    }

    .sentence-hint {
        display: none;
    }

    .sentence-answer {
        margin: 0 14px 0 61px;
        padding-top: 15px;
    }
}

@media (max-width: 390px) {
    .deck-heading-row {
        display: block;
    }

    .deck-progress {
        display: inline-flex;
        align-items: baseline;
        gap: 5px;
        margin-top: 14px;
        text-align: left;
    }

    .deck-progress strong,
    .deck-progress span {
        display: inline;
    }

    .study-mode-switch {
        width: calc(100% - 32px);
    }

    .vocabulary-view-switch {
        width: calc(100% - 32px);
    }

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

    .sentence-actions .deck-progress {
        display: flex;
        grid-column: 1 / -1;
        justify-content: center;
        width: 100%;
        margin: 2px 0 0;
    }
}

@media (prefers-reduced-motion: reduce) {
    .card-inner,
    .category-button,
    .study-app-link img,
    .sentence-card,
    .study-control {
        transition: none;
    }
}