/* ============================================================
   hw-checker — design system
   editorial / quiet luxury / swiss minimalism
   ============================================================ */

:root {
    /* palette — warm paper + ink */
    --paper:        #FAF8F3;
    --paper-edge:   #F2EFE7;
    --ink:          #161513;
    --ink-soft:     #4A4641;
    --ink-mute:     #8C857B;
    --ink-faint:    #BFB8AC;
    --hairline:     rgba(22, 21, 19, 0.10);
    --hairline-strong: rgba(22, 21, 19, 0.22);

    /* accents */
    --gold:         #7A6B3F;
    --gold-soft:    #B5A777;

    /* state colors — used sparingly, as backgrounds at very low opacity */
    --good:         #1F7A3A;
    --good-strong:  #156B30;
    --good-bg:      rgba(31, 122, 58, 0.10);
    --good-edge:    rgba(31, 122, 58, 0.55);

    --warn:         #8C6F1F;
    --warn-bg:      rgba(140, 111, 31, 0.08);
    --warn-edge:    rgba(140, 111, 31, 0.35);

    --bad:          #8B2E2E;
    --bad-bg:       rgba(139, 46, 46, 0.06);
    --bad-edge:     rgba(139, 46, 46, 0.30);

    /* spacing scale, golden-ratio-ish */
    --s1:  4px;
    --s2:  8px;
    --s3:  12px;
    --s4:  16px;
    --s5:  24px;
    --s6:  32px;
    --s7:  48px;
    --s8:  64px;
    --s9:  96px;
    --s10: 128px;

    /* typography */
    --font-display: "Cormorant Garamond", "Times New Roman", serif;
    --font-body:    "Geist", -apple-system, BlinkMacSystemFont, sans-serif;
    --font-num:     "Geist", ui-monospace, monospace;

    /* motion */
    --ease:    cubic-bezier(0.4, 0, 0.2, 1);
    --ease-in: cubic-bezier(0.4, 0, 1, 1);
    --ease-out:cubic-bezier(0, 0, 0.2, 1);
    --dur-1:   140ms;
    --dur-2:   240ms;
    --dur-3:   420ms;

    /* layout */
    --measure: 38rem;
}

/* ============================================================
   reset
   ============================================================ */

*, *::before, *::after { box-sizing: border-box; }

html, body {
    margin: 0;
    padding: 0;
    background: var(--paper);
    color: var(--ink);
    font-family: var(--font-body);
    font-weight: 400;
    font-size: 16px;
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-rendering: optimizeLegibility;
    font-feature-settings: "ss01", "cv11";
}

body {
    min-height: 100dvh;
    overflow-x: hidden;
}

a { color: inherit; text-decoration: none; }

button {
    font: inherit;
    color: inherit;
    background: none;
    border: none;
    padding: 0;
    margin: 0;
    cursor: pointer;
}

input, textarea {
    font: inherit;
    color: inherit;
    background: none;
    border: none;
    outline: none;
    padding: 0;
    margin: 0;
}

::selection {
    background: var(--ink);
    color: var(--paper);
}

/* ============================================================
   typography utilities
   ============================================================ */

.display {
    font-family: var(--font-display);
    font-weight: 400;
    font-style: italic;
    line-height: 0.95;
    letter-spacing: -0.01em;
}

.numeral {
    font-family: var(--font-display);
    font-weight: 400;
    font-style: italic;
    font-feature-settings: "lnum", "tnum";
    color: var(--ink);
}

.eyebrow {
    font-family: var(--font-body);
    font-weight: 500;
    font-size: 11px;
    letter-spacing: 0.18em;
    text-transform: uppercase;
    color: var(--ink-mute);
}

.meta {
    font-family: var(--font-body);
    font-size: 13px;
    color: var(--ink-mute);
    letter-spacing: 0.01em;
}

/* ============================================================
   shared chrome
   ============================================================ */

.frame {
    max-width: 56rem;
    margin: 0 auto;
    padding: var(--s5) var(--s5) var(--s9);
}

@media (max-width: 720px) {
    .frame { padding: var(--s4) var(--s4) var(--s8); }
}

.topbar {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    padding: var(--s5) var(--s5) 0;
    max-width: 56rem;
    margin: 0 auto;
}

@media (max-width: 720px) {
    .topbar { padding: var(--s4) var(--s4) 0; }
}

.brand {
    font-family: var(--font-display);
    font-style: italic;
    font-weight: 400;
    font-size: 22px;
    letter-spacing: -0.01em;
    color: var(--ink);
}

.brand-sub {
    font-family: var(--font-body);
    font-weight: 500;
    font-size: 10px;
    letter-spacing: 0.24em;
    text-transform: uppercase;
    color: var(--ink-mute);
    margin-left: var(--s3);
}

.nav {
    display: flex;
    gap: var(--s4);
}

.nav-link {
    font-family: var(--font-body);
    font-size: 13px;
    color: var(--ink-mute);
    transition: color var(--dur-1) var(--ease);
    position: relative;
    padding-bottom: 2px;
}

.nav-link:hover { color: var(--ink); }

.nav-link[aria-current="page"] {
    color: var(--ink);
}

.nav-link[aria-current="page"]::after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    bottom: 0;
    height: 1px;
    background: var(--ink);
}

/* ============================================================
   buttons
   ============================================================ */

.btn {
    font-family: var(--font-body);
    font-weight: 500;
    font-size: 14px;
    letter-spacing: 0.02em;
    padding: var(--s3) var(--s5);
    border-radius: 999px;
    transition:
        background var(--dur-1) var(--ease),
        color var(--dur-1) var(--ease),
        transform var(--dur-1) var(--ease);
    will-change: transform;
}

.btn-primary {
    background: var(--ink);
    color: var(--paper);
}

.btn-primary:hover { background: #000; }
.btn-primary:active { transform: scale(0.98); }
.btn-primary:disabled {
    background: var(--hairline-strong);
    color: var(--ink-mute);
    cursor: not-allowed;
}

.btn-ghost {
    color: var(--ink-mute);
    padding: var(--s2) var(--s3);
}

.btn-ghost:hover { color: var(--ink); }

/* ============================================================
   field — generic
   ============================================================ */

.field {
    display: flex;
    flex-direction: column;
    gap: var(--s2);
}

.field-label {
    font-family: var(--font-body);
    font-weight: 500;
    font-size: 11px;
    letter-spacing: 0.18em;
    text-transform: uppercase;
    color: var(--ink-mute);
}

.field-input,
.field-textarea {
    width: 100%;
    background: transparent;
    border-bottom: 1px solid var(--hairline-strong);
    padding: var(--s3) 0;
    font-size: 17px;
    font-family: var(--font-body);
    color: var(--ink);
    transition: border-color var(--dur-1) var(--ease);
}

.field-input:focus,
.field-textarea:focus {
    border-bottom-color: var(--ink);
}

.field-textarea {
    resize: vertical;
    min-height: 16rem;
    line-height: 1.55;
}

/* ============================================================
   toast
   ============================================================ */

.toast {
    position: fixed;
    left: 50%;
    bottom: var(--s6);
    transform: translateX(-50%) translateY(20px);
    background: var(--ink);
    color: var(--paper);
    padding: var(--s3) var(--s5);
    border-radius: 999px;
    font-size: 13px;
    letter-spacing: 0.02em;
    pointer-events: none;
    opacity: 0;
    transition:
        opacity var(--dur-2) var(--ease),
        transform var(--dur-2) var(--ease);
    z-index: 100;
}

.toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
}

/* ============================================================
   error inline
   ============================================================ */

.err {
    font-family: var(--font-body);
    font-size: 13px;
    color: var(--bad);
    letter-spacing: 0.01em;
    min-height: 1.5em;
}

/* ============================================================
   page-login
   ============================================================ */

.login-page {
    min-height: 100dvh;
    display: grid;
    place-items: center;
    padding: var(--s5);
    position: relative;
    overflow: hidden;
}

.login-page::before {
    content: "";
    position: absolute;
    inset: 0;
    background:
        radial-gradient(ellipse 70% 50% at 50% 0%,
            rgba(122, 107, 63, 0.06),
            transparent 70%);
    pointer-events: none;
}

.login-card {
    width: 100%;
    max-width: 24rem;
    position: relative;
    z-index: 1;
    display: flex;
    flex-direction: column;
    gap: var(--s6);
}

.login-mark {
    display: flex;
    align-items: baseline;
    gap: var(--s3);
}

.login-mark .display {
    font-size: 44px;
    line-height: 1;
}

.login-mark .eyebrow {
    margin-bottom: 4px;
}

.login-line {
    height: 1px;
    background: var(--hairline);
    margin: var(--s2) 0;
}

.login-form {
    display: flex;
    flex-direction: column;
    gap: var(--s5);
}

/* ============================================================
   page-create
   ============================================================ */

.create-hero {
    display: flex;
    flex-direction: column;
    gap: var(--s3);
    margin-top: var(--s7);
    margin-bottom: var(--s6);
}

.create-hero .display {
    font-size: clamp(40px, 6vw, 64px);
    line-height: 0.95;
}

.create-hero .meta {
    max-width: 30rem;
}

.create-textarea {
    width: 100%;
    background: var(--paper-edge);
    border: 1px solid var(--hairline);
    border-radius: 4px;
    padding: var(--s5);
    min-height: 22rem;
    font-size: 16px;
    line-height: 1.55;
    color: var(--ink);
    font-family: var(--font-body);
    transition: border-color var(--dur-2) var(--ease), background var(--dur-2) var(--ease);
    resize: vertical;
}

.create-textarea:focus {
    border-color: var(--hairline-strong);
    background: var(--paper);
}

.create-actions {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: var(--s5);
    gap: var(--s4);
}

.create-actions .meta {
    flex: 1;
}

/* result card after creating homework */
.created-card {
    margin-top: var(--s7);
    padding: var(--s6);
    background: var(--paper-edge);
    border: 1px solid var(--hairline);
    border-radius: 4px;
    display: flex;
    flex-direction: column;
    gap: var(--s4);
    animation: fade-up var(--dur-3) var(--ease-out) both;
}

.created-link {
    display: flex;
    align-items: center;
    gap: var(--s3);
    padding: var(--s4);
    background: var(--paper);
    border: 1px solid var(--hairline);
    border-radius: 4px;
    font-family: var(--font-num);
    font-size: 15px;
    word-break: break-all;
}

.created-link button {
    flex-shrink: 0;
    color: var(--ink-mute);
    transition: color var(--dur-1) var(--ease);
}

.created-link button:hover { color: var(--ink); }

@keyframes fade-up {
    from { opacity: 0; transform: translateY(8px); }
    to   { opacity: 1; transform: translateY(0); }
}

/* ============================================================
   page-dashboard
   ============================================================ */

.dash-hero {
    display: flex;
    flex-direction: column;
    gap: var(--s3);
    margin-top: var(--s7);
    margin-bottom: var(--s7);
}

.dash-hero .display {
    font-size: clamp(40px, 6vw, 64px);
}

.dash-actions {
    margin-top: var(--s4);
}

.dash-list {
    border-top: 1px solid var(--hairline);
}

.dash-row {
    display: grid;
    grid-template-columns: 5rem 1fr auto;
    align-items: baseline;
    gap: var(--s4);
    padding: var(--s5) 0;
    border-bottom: 1px solid var(--hairline);
    transition: background var(--dur-1) var(--ease);
    position: relative;
}

.dash-row::before {
    content: "";
    position: absolute;
    inset: 0 calc(-1 * var(--s5));
    background: transparent;
    transition: background var(--dur-1) var(--ease);
    z-index: -1;
}

.dash-row:hover::before { background: var(--paper-edge); }

.dash-row-num {
    font-family: var(--font-display);
    font-style: italic;
    font-size: 36px;
    line-height: 1;
    color: var(--ink-faint);
}

.dash-row-main {
    display: flex;
    flex-direction: column;
    gap: var(--s2);
    min-width: 0;
}

.dash-row-slug {
    font-family: var(--font-num);
    font-size: 15px;
    color: var(--ink);
    word-break: break-all;
    letter-spacing: 0.02em;
}

.dash-row-meta {
    display: flex;
    gap: var(--s4);
    flex-wrap: wrap;
}

.stat {
    display: inline-flex;
    align-items: baseline;
    gap: var(--s1);
    font-family: var(--font-body);
    font-size: 12px;
    color: var(--ink-mute);
    letter-spacing: 0.04em;
}

.stat-num {
    font-family: var(--font-display);
    font-style: italic;
    font-size: 18px;
    color: var(--ink);
    line-height: 1;
}

.stat--good .stat-num { color: var(--good-strong); font-weight: 500; }
.stat--warn .stat-num { color: var(--warn); }
.stat--bad  .stat-num { color: var(--bad); }

.dash-row-arrow {
    color: var(--ink-mute);
    transition: transform var(--dur-1) var(--ease), color var(--dur-1) var(--ease);
}

.dash-row:hover .dash-row-arrow {
    color: var(--ink);
    transform: translateX(2px);
}

.dash-empty {
    text-align: center;
    padding: var(--s9) 0;
    color: var(--ink-mute);
    font-style: italic;
    font-family: var(--font-display);
    font-size: 22px;
}

@media (max-width: 560px) {
    .dash-row {
        grid-template-columns: 3rem 1fr;
        grid-template-rows: auto auto;
    }
    .dash-row-arrow { display: none; }
    .dash-row-num { font-size: 28px; }
}

/* ============================================================
   page-detail (teacher view of one homework)
   ============================================================ */

.detail-hero {
    margin-top: var(--s7);
    margin-bottom: var(--s6);
    display: flex;
    flex-direction: column;
    gap: var(--s3);
}

.detail-slug {
    font-family: var(--font-num);
    font-size: 14px;
    color: var(--ink-mute);
    letter-spacing: 0.04em;
}

.detail-summary {
    display: flex;
    gap: var(--s6);
    flex-wrap: wrap;
    margin-top: var(--s2);
}

.detail-list {
    margin-top: var(--s6);
}

/* shared with student .sentence (see below) */

/* ============================================================
   page-student — the main page
   ============================================================ */

.student-page {
    background:
        radial-gradient(ellipse 80% 40% at 50% -10%,
            rgba(122, 107, 63, 0.04),
            transparent 60%),
        var(--paper);
}

.student-hero {
    display: flex;
    flex-direction: column;
    gap: var(--s3);
    margin-top: var(--s6);
    margin-bottom: var(--s7);
}

.student-hero .eyebrow {
    display: flex;
    gap: var(--s3);
    align-items: center;
}

.student-hero .eyebrow .sep {
    width: 16px;
    height: 1px;
    background: var(--ink-mute);
    display: inline-block;
}

.student-hero h1 {
    font-family: var(--font-display);
    font-weight: 400;
    font-style: italic;
    font-size: clamp(40px, 9vw, 64px);
    line-height: 0.95;
    margin: 0;
    color: var(--ink);
}

.student-progress {
    display: flex;
    align-items: baseline;
    gap: var(--s3);
    margin-top: var(--s4);
    font-family: var(--font-body);
    font-size: 13px;
    color: var(--ink-mute);
    letter-spacing: 0.02em;
}

.student-progress .numeral {
    font-size: 28px;
    color: var(--ink);
}

.student-progress .progress-rule {
    flex: 1;
    height: 1px;
    background: var(--hairline);
    position: relative;
    margin: 0 var(--s2);
    align-self: center;
}

.student-progress .progress-fill {
    position: absolute;
    inset: 0 auto 0 0;
    background: var(--ink);
    width: 0%;
    transition: width var(--dur-3) var(--ease);
}

/* ----------- sentence (the central unit) ----------- */

.sentences {
    display: flex;
    flex-direction: column;
    gap: var(--s6);
    margin-top: var(--s6);
}

.sentence {
    display: grid;
    grid-template-columns: 3rem 1fr;
    gap: var(--s4);
    align-items: start;
    opacity: 0;
    transform: translateY(8px);
    animation: fade-up var(--dur-3) var(--ease-out) both;
}

@media (max-width: 560px) {
    .sentence {
        grid-template-columns: 2.5rem 1fr;
        gap: var(--s3);
    }
}

.sentence-num {
    font-family: var(--font-display);
    font-style: italic;
    font-size: 36px;
    line-height: 1;
    color: var(--ink-faint);
    transition: color var(--dur-2) var(--ease);
    padding-top: 2px;
    position: relative;
}

.sentence[data-state="checking"] .sentence-num,
.sentence[data-state="correct"]  .sentence-num,
.sentence[data-state="warn"]     .sentence-num,
.sentence[data-state="error"]    .sentence-num {
    color: var(--ink);
}

.sentence-body {
    display: flex;
    flex-direction: column;
    gap: var(--s3);
    min-width: 0;
}

.sentence-ru {
    font-family: var(--font-display);
    font-style: italic;
    font-weight: 400;
    font-size: 22px;
    line-height: 1.3;
    color: var(--ink);
    letter-spacing: -0.005em;
}

/* the input — the centerpiece of the experience */
.sentence-input {
    width: 100%;
    background: transparent;
    border: none;
    border-bottom: 1px solid var(--hairline-strong);
    padding: var(--s3) 0;
    font-family: var(--font-body);
    font-size: 17px;
    line-height: 1.45;
    color: var(--ink);
    transition:
        border-bottom-color var(--dur-2) var(--ease),
        padding var(--dur-2) var(--ease);
}

.sentence-input::placeholder {
    color: var(--ink-faint);
    font-style: italic;
    font-family: var(--font-display);
}

.sentence-input:focus {
    border-bottom-color: var(--ink);
}

.sentence-input:disabled {
    color: var(--ink);
    -webkit-text-fill-color: var(--ink);
    opacity: 1;
    cursor: default;
}

/* status states on the whole sentence */
.sentence[data-state="checking"] .sentence-input {
    border-bottom-color: var(--gold-soft);
}

.sentence[data-state="correct"] .sentence-input {
    border-bottom-color: var(--good);
    border-bottom-width: 2px;
    color: var(--good-strong);
    -webkit-text-fill-color: var(--good-strong);
    font-weight: 500;
}

.sentence[data-state="warn"] .sentence-input,
.sentence[data-state="error"] .sentence-input {
    /* hide the original input visually since we show the segmented diff */
    display: none;
}

/* segmented diff result (replaces input when not correct) */
.sentence-diff {
    font-family: var(--font-body);
    font-size: 17px;
    line-height: 1.45;
    padding: var(--s3) 0;
    border-bottom: 1px solid var(--hairline-strong);
    color: var(--ink);
    animation: fade-up var(--dur-2) var(--ease-out) both;
}

.sentence[data-state="warn"] .sentence-diff {
    border-bottom-color: var(--warn-edge);
}

.sentence[data-state="error"] .sentence-diff {
    border-bottom-color: var(--bad-edge);
}

.seg {
    transition: background var(--dur-2) var(--ease);
}

.seg-ok {
    color: var(--ink);
}

/* when the whole sentence is correct we drop a subtle leaf-mark next to number */
.sentence[data-state="correct"] .sentence-mark::before {
    content: "";
    display: block;
    width: 8px;
    height: 8px;
    margin: 3px;
    border-radius: 50%;
    background: var(--good);
    box-shadow: 0 0 0 4px var(--good-bg);
}

.seg-warn {
    background: var(--warn-bg);
    color: var(--warn);
    padding: 1px 2px;
    border-radius: 2px;
    box-decoration-break: clone;
    -webkit-box-decoration-break: clone;
    font-weight: 500;
}

.seg-error {
    background: var(--bad-bg);
    color: var(--bad);
    padding: 1px 2px;
    border-radius: 2px;
    box-decoration-break: clone;
    -webkit-box-decoration-break: clone;
    text-decoration: line-through;
    text-decoration-color: var(--bad-edge);
    text-decoration-thickness: 1px;
    font-weight: 500;
}

/* reason text under diff */
.sentence-reason {
    font-family: var(--font-body);
    font-size: 13px;
    line-height: 1.5;
    color: var(--ink-mute);
    letter-spacing: 0.01em;
    padding-left: var(--s3);
    border-left: 1px solid var(--hairline-strong);
    margin-top: var(--s2);
    animation: fade-up var(--dur-2) var(--ease-out) both;
    animation-delay: 80ms;
}

.sentence[data-state="warn"] .sentence-reason {
    border-left-color: var(--warn-edge);
    color: var(--warn);
}

.sentence[data-state="error"] .sentence-reason {
    border-left-color: var(--bad-edge);
    color: var(--bad);
}

/* loading spinner — single arc, very thin, slow rotation */
.sentence-spinner {
    position: absolute;
    top: 8px;
    left: -22px;
    width: 14px;
    height: 14px;
    opacity: 0;
    transition: opacity var(--dur-2) var(--ease);
}

.sentence[data-state="checking"] .sentence-spinner {
    opacity: 1;
}

.sentence-spinner svg {
    width: 100%;
    height: 100%;
    animation: spin 1.2s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* done — small mark next to number */
.sentence-mark {
    position: absolute;
    top: 8px;
    left: -22px;
    width: 14px;
    height: 14px;
    opacity: 0;
    transition: opacity var(--dur-2) var(--ease);
}

.sentence[data-state="correct"] .sentence-mark,
.sentence[data-state="warn"]    .sentence-mark,
.sentence[data-state="error"]   .sentence-mark {
    opacity: 1;
}

@media (max-width: 560px) {
    .sentence-spinner,
    .sentence-mark { left: -16px; }
}

/* ----------- finale: when everything is answered ----------- */

.finale {
    margin-top: var(--s9);
    text-align: center;
    padding: var(--s7) var(--s5);
    border-top: 1px solid var(--hairline);
    animation: fade-up var(--dur-3) var(--ease-out) both;
}

.finale .display {
    font-size: clamp(32px, 5vw, 48px);
    margin-bottom: var(--s4);
}

.finale .meta {
    max-width: 24rem;
    margin: 0 auto;
}

.finale-summary {
    display: flex;
    justify-content: center;
    gap: var(--s7);
    margin-top: var(--s6);
    flex-wrap: wrap;
}

.finale-summary .stat-num {
    font-size: 44px;
}

.finale-summary .stat {
    flex-direction: column;
    align-items: center;
    gap: var(--s2);
}

.finale-summary .stat span:last-child {
    font-size: 11px;
    letter-spacing: 0.18em;
    text-transform: uppercase;
}

/* loading state for the whole page */
.page-loading {
    display: grid;
    place-items: center;
    min-height: 60dvh;
    color: var(--ink-mute);
    font-family: var(--font-display);
    font-style: italic;
    font-size: 22px;
    letter-spacing: -0.005em;
}

.page-error {
    display: grid;
    place-items: center;
    min-height: 60dvh;
    text-align: center;
    color: var(--ink);
    padding: var(--s5);
}

.page-error .display {
    font-size: clamp(32px, 5vw, 48px);
    margin-bottom: var(--s3);
}

/* ============================================================
   prepod detail — student answers visible to teacher
   ============================================================ */

.detail-answer {
    display: grid;
    grid-template-columns: 3rem 1fr;
    gap: var(--s4);
    padding: var(--s5) 0;
    border-bottom: 1px solid var(--hairline);
    align-items: start;
}

.detail-answer-num {
    font-family: var(--font-display);
    font-style: italic;
    font-size: 32px;
    line-height: 1;
    color: var(--ink-faint);
}

.detail-answer-body {
    display: flex;
    flex-direction: column;
    gap: var(--s3);
    min-width: 0;
}

.detail-answer-ru {
    font-family: var(--font-display);
    font-style: italic;
    font-size: 18px;
    color: var(--ink-soft);
    line-height: 1.4;
}

.detail-answer-en-empty {
    font-family: var(--font-body);
    font-size: 14px;
    color: var(--ink-faint);
    font-style: italic;
}

.detail-answer-verdict {
    display: inline-flex;
    align-items: center;
    gap: var(--s2);
    font-size: 11px;
    letter-spacing: 0.18em;
    text-transform: uppercase;
    color: var(--ink-mute);
    margin-top: var(--s1);
}

.detail-answer-verdict::before {
    content: "";
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--ink-faint);
}

.detail-answer-verdict.v-correct::before { background: var(--good); }
.detail-answer-verdict.v-warn::before    { background: var(--warn); }
.detail-answer-verdict.v-error::before   { background: var(--bad); }