:root {
    --bg: #101820;
    --panel: #18222d;
    --line: #314152;
    --text: #e7eef5;
    --muted: #93a4b5;
    --amber: #e2b13c;
    --cyan: #6ec4d4;
    --ok: #6fbf73;
    --bad: #e06b6b;
    --shadow: 0 18px 40px rgba(0, 0, 0, 0.28);
}

* { box-sizing: border-box; }

html, body {
    margin: 0;
    min-height: 100%;
    background:
        radial-gradient(1200px 500px at 10% -10%, #1c3348 0%, transparent 55%),
        var(--bg);
    color: var(--text);
    font-family: "Segoe UI", "Trebuchet MS", sans-serif;
}

#app {
    max-width: 920px;
    margin: 0 auto;
    padding: 28px 20px 48px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 16px;
    margin-bottom: 22px;
}

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

.brand-mark {
    display: grid;
    place-items: center;
    width: 54px;
    height: 54px;
    border: 1px solid var(--amber);
    color: var(--amber);
    background: transparent;
    font: inherit;
    font-weight: 700;
    letter-spacing: 0.08em;
    cursor: pointer;
}

.brand-mark:hover {
    background: #3a2f12;
}

.brand h1, .brand p, h2 {
    margin: 0;
}

.brand h1 {
    font-size: 1.35rem;
    font-weight: 650;
}

.brand p, .muted, .hud-label, .mode-kicker, .lesson-row small {
    color: var(--muted);
}

.hud {
    border: 1px solid var(--line);
    padding: 8px 12px;
    min-width: 120px;
    text-align: right;
    background: #121c26;
}

.hud-label {
    display: block;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.hud-value {
    font-family: Consolas, "Courier New", monospace;
    color: var(--cyan);
    font-size: 1.15rem;
}

.panel {
    background: var(--panel);
    border: 1px solid var(--line);
    box-shadow: var(--shadow);
    padding: 28px;
}

.panel.fill {
    flex: 1;
    display: flex;
    min-height: 0;
}

.stack { display: grid; gap: 16px; }

.session {
    display: grid;
    grid-template-rows: auto auto minmax(0, 1fr) auto;
    gap: 14px;
    width: 100%;
    flex: 1;
    min-height: 0;
}

.session-body {
    min-height: 0;
    overflow: auto;
    display: grid;
    align-content: start;
    gap: 16px;
    padding-right: 4px;
}

.session-footer {
    border-top: 1px solid var(--line);
    padding-top: 14px;
}

.lead {
    margin: 0;
    font-size: 1.05rem;
}

.mode-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 14px;
}

.mode-card, .lesson-row, .answer, .primary, .ghost, .link {
    font: inherit;
    color: inherit;
    cursor: pointer;
}

.mode-card {
    text-align: left;
    background: #121c26;
    border: 1px solid var(--line);
    padding: 18px;
    display: grid;
    gap: 8px;
}

.mode-card:hover, .lesson-row:hover, .answer:hover:not(:disabled) {
    border-color: var(--amber);
}

.mode-card.secondary { border-color: #3b556b; }
.mode-kicker {
    text-transform: uppercase;
    letter-spacing: 0.1em;
    font-size: 0.75rem;
}

.lesson-list { display: grid; gap: 8px; }

.lesson-row {
    display: flex;
    gap: 12px;
    align-items: center;
    width: 100%;
    background: #121c26;
    border: 1px solid var(--line);
    padding: 12px;
    text-align: left;
}

.lesson-num {
    font-family: Consolas, "Courier New", monospace;
    color: var(--amber);
    width: 42px;
}

.lesson-body { display: grid; }
.lesson-body small { margin-top: 2px; }

.meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 12px;
    color: var(--muted);
    font-size: 0.95rem;
    flex-wrap: wrap;
}

.jump-row {
    display: grid;
    grid-template-columns: minmax(80px, 1fr) auto;
    align-items: center;
    gap: 12px;
    color: var(--muted);
}

.jump-range {
    width: 100%;
    accent-color: var(--amber);
}

.toggle {
    display: flex;
    align-items: center;
    gap: 10px;
    cursor: pointer;
    user-select: none;
    color: var(--text);
}

.toggle input {
    position: absolute;
    opacity: 0;
    pointer-events: none;
}

.toggle-track {
    width: 42px;
    height: 24px;
    border-radius: 99px;
    background: #0d141b;
    border: 1px solid var(--line);
    position: relative;
    flex-shrink: 0;
}

.toggle-track::after {
    content: "";
    position: absolute;
    top: 2px;
    left: 2px;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: var(--muted);
    transition: transform 0.15s ease, background 0.15s ease;
}

.toggle input:checked + .toggle-track {
    border-color: var(--amber);
    background: #3a2f12;
}

.toggle input:checked + .toggle-track::after {
    transform: translateX(18px);
    background: var(--amber);
}

.progress {
    height: 6px;
    background: #0d141b;
    border: 1px solid var(--line);
}

.progress i {
    display: block;
    height: 100%;
    background: var(--amber);
}

.question {
    font-size: 1.2rem;
    line-height: 1.45;
    font-weight: 600;
}

.answers {
    display: grid;
    gap: 8px;
    grid-auto-rows: minmax(58px, auto);
}

.answer {
    display: flex;
    gap: 12px;
    align-items: flex-start;
    text-align: left;
    background: #121c26;
    border: 1px solid var(--line);
    padding: 12px;
    min-height: 58px;
}

.answer .symbol {
    color: var(--cyan);
    font-family: Consolas, "Courier New", monospace;
    min-width: 1.2em;
}

.answer.readonly { cursor: default; }
.answer.selected { border-color: var(--cyan); }
.answer.correct { border-color: var(--ok); background: #16301c; }
.answer.wrong { border-color: var(--bad); background: #311818; }
.answer:disabled { cursor: default; }

.actions {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

.actions.split {
    justify-content: space-between;
    align-items: center;
}

.primary, .ghost {
    border: 1px solid var(--amber);
    padding: 10px 16px;
    background: var(--amber);
    color: #1a1406;
    font-weight: 650;
}

.ghost {
    background: transparent;
    color: var(--text);
    border-color: var(--line);
}

.ghost:disabled, .primary:disabled {
    opacity: 0.4;
    cursor: default;
}

.link {
    background: none;
    border: 0;
    color: var(--cyan);
    padding: 0;
    width: fit-content;
}

.pass, .error {
    margin: 0;
    padding: 10px 12px;
    border: 1px solid;
}

.pass.ok { border-color: var(--ok); color: var(--ok); }
.pass.bad, .error { border-color: var(--bad); color: var(--bad); }

.toast {
    position: fixed;
    top: 24px;
    right: 24px;
    z-index: 50;
    min-width: 240px;
    max-width: min(360px, calc(100vw - 32px));
    padding: 14px 18px;
    background: #121c26;
    box-shadow: var(--shadow);
    font-weight: 650;
    pointer-events: none;
}

.toast::after {
    content: "";
    position: absolute;
    top: -7px;
    right: 22px;
    width: 12px;
    height: 12px;
    transform: rotate(45deg);
    background: inherit;
    border-left: 1px solid;
    border-top: 1px solid;
}

.toast.ok {
    background: #16301c;
    border: 1px solid var(--ok);
    color: var(--ok);
}

.toast.bad {
    background: #311818;
    border: 1px solid var(--bad);
    color: var(--bad);
}

.toast.ok::after { border-color: var(--ok); }
.toast.bad::after { border-color: var(--bad); }

.toast-enter-active,
.toast-leave-active {
    transition: opacity 0.22s ease, transform 0.22s ease;
}

.toast-enter-from,
.toast-leave-to {
    opacity: 0;
    transform: translateY(-8px);
}

.result .score-line { font-size: 1.1rem; margin: 0; }
.lesson-title { margin: 0; color: var(--amber); }

.search {
    display: grid;
    gap: 12px;
    padding-top: 8px;
    border-top: 1px solid var(--line);
}

.search-label {
    color: var(--muted);
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.search-row {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto auto;
    gap: 10px;
}

.search-input {
    width: 100%;
    background: #121c26;
    border: 1px solid var(--line);
    color: var(--text);
    padding: 10px 12px;
    font: inherit;
}

.search-input:focus {
    outline: none;
    border-color: var(--amber);
}

.search-hits {
    display: grid;
    gap: 10px;
}

.search-hit {
    background: #121c26;
    border: 1px solid var(--line);
    padding: 14px;
    display: grid;
    gap: 8px;
}

.search-lesson {
    color: var(--amber);
    font-size: 0.85rem;
}

.search-question,
.search-answer {
    margin: 0;
}

.search-answer {
    color: var(--ok);
}

@media (max-width: 640px) {
    .panel { padding: 18px; }
    .topbar { align-items: flex-start; }
}