/* ── Reset ── */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
input, button { font-family: inherit; }

/* ── Touch optimisation ── */
button {
    -webkit-tap-highlight-color: transparent;
    touch-action: manipulation;
    user-select: none;
}
input { -webkit-tap-highlight-color: transparent; }

/* ── Variables ── */
:root {
    --bg:        #07070f;
    --surface:   #0e0e1a;
    --surface2:  #161626;
    --border:    #1e1e32;
    --border2:   #2a2a42;
    --accent:    #7c6dfa;
    --accent2:   #fa6d8f;
    --text:      #eeeef8;
    --muted:     #52527a;
    --green:     #4ade80;
    --red:       #f87171;
    --yellow:    #fbbf24;
}

/* ── Base ── */
body {
    background-color: var(--bg);
    background-image:
        radial-gradient(ellipse 80% 50% at 50% -10%, rgba(124, 109, 250, 0.12), transparent),
        radial-gradient(circle at 1px 1px, rgba(124,109,250,0.07) 1px, transparent 0);
    background-size: 100% 100%, 28px 28px;
    color: var(--text);
    font-family: 'Space Grotesk', 'Segoe UI', system-ui, sans-serif;
    min-height: 100vh;
    min-height: 100dvh;               /* iOS Safari dynamic toolbar fix */
    display: flex;
    align-items: center;
    justify-content: center;
    padding: env(safe-area-inset-top)  env(safe-area-inset-right)
             env(safe-area-inset-bottom) env(safe-area-inset-left);
}

/* ── Screens ── */
.screen {
    display: none;
    flex-direction: column;
    gap: 1rem;
    width: 100%;
    max-width: 440px;
    padding: 1.75rem 1.5rem;
    animation: fadeUp 0.25s ease;
    position: relative;
    z-index: 2;
}
.screen.active { display: flex; }

@keyframes fadeUp {
    from { opacity: 0; transform: translateY(12px); }
    to   { opacity: 1; transform: translateY(0); }
}

/* ── Logo ── */
.logo { margin-bottom: 0; }
.logo h1 {
    font-size: 3rem;
    font-weight: 900;
    letter-spacing: -3px;
    text-align: center;
    background: linear-gradient(135deg, #a78bfa, var(--accent), var(--accent2));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: logoPulse 2.8s ease-in-out infinite;
}

@keyframes logoPulse {
    0%, 100% {
        filter: drop-shadow(0 0 10px rgba(124, 109, 250, 0.4))
                drop-shadow(0 0 30px rgba(124, 109, 250, 0.15));
    }
    50% {
        filter: drop-shadow(0 0 22px rgba(124, 109, 250, 0.9))
                drop-shadow(0 0 70px rgba(250, 109, 143, 0.5));
        opacity: 0.88;
    }
}

.logo p {
    text-align: center;
    color: var(--muted);
    font-size: 0.75rem;
    margin-top: 0.1rem;
    letter-spacing: 0.3px;
}

/* ── Section label ── */
.section { display: flex; flex-direction: column; gap: 0.5rem; }
h2 {
    font-size: 0.65rem;
    letter-spacing: 3px;
    text-transform: uppercase;
    color: var(--muted);
}

/* ── Settings row (Difficulty + Time side by side) ── */
.settings-row {
    display: flex;
    gap: 0.75rem;
}
.settings-row .section { flex: 1; }

/* ── Mode buttons ── */
.modes {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.4rem;
}
.mode-btn {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 0.3rem;
    padding: 0.75rem 0.85rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 12px;
    color: var(--text);
    cursor: pointer;
    transition: border-color 0.15s, background 0.15s;
    text-align: left;
}
.mode-btn:hover  { border-color: var(--accent); }
.mode-btn.active {
    border-color: var(--accent);
    background: rgba(124, 109, 250, 0.1);
}
.mode-icon { font-size: 1.2rem; }
.mode-name { display: block; font-weight: 700; font-size: 0.88rem; }
.mode-desc { display: block; font-size: 0.67rem; color: var(--muted); line-height: 1.3; }

/* ── Pill rows ── */
.pill-row { display: flex; gap: 0.4rem; flex-wrap: wrap; }
.pill-btn {
    flex: 1;
    min-width: 2.8rem;
    min-height: 40px;         /* touch target */
    padding: 0.55rem 0.4rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--muted);
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.15s;
}
.pill-btn:hover { border-color: var(--accent); color: var(--text); }
.pill-btn.active {
    border-color: var(--accent);
    color: var(--accent);
    background: rgba(124, 109, 250, 0.12);
    font-weight: 700;
}


/* ── Primary button ── */
.btn-primary {
    width: 100%;
    padding: 0.95rem;
    background: linear-gradient(135deg, var(--accent), #9d8ffb);
    border: none;
    border-radius: 12px;
    color: #fff;
    font-size: 1rem;
    font-weight: 800;
    letter-spacing: 3px;
    cursor: pointer;
    box-shadow: 0 4px 24px rgba(124, 109, 250, 0.35);
    transition: transform 0.15s, box-shadow 0.15s;
}
.btn-primary:hover  { transform: translateY(-2px); box-shadow: 0 6px 30px rgba(124, 109, 250, 0.5); }
.btn-primary:active { transform: translateY(0); }

/* ── Ghost button ── */
.btn-ghost {
    background: none;
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--muted);
    padding: 0.5rem 1.2rem;
    font-size: 0.85rem;
    cursor: pointer;
    align-self: center;
    transition: border-color 0.15s, color 0.15s;
}
.btn-ghost:hover { border-color: var(--red); color: var(--red); }

/* ── Action row (START + DUEL) ── */
.action-row {
    display: flex;
    gap: 0.5rem;
    align-items: stretch;
}
.action-row .btn-primary { flex: 1; }
.action-row .btn-duel {
    width: auto;
    padding: 0.95rem 1.1rem;
    font-size: 1.2rem;
    letter-spacing: 0;
    flex-shrink: 0;
}

/* ── Best score ── */
.best-label { text-align: center; color: var(--muted); font-size: 0.82rem; }
.best-label strong { color: var(--text); }

/* ── Countdown overlay ── */
.countdown-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(8, 8, 16, 0.9);
    align-items: center;
    justify-content: center;
    z-index: 100;
    backdrop-filter: blur(6px);
}
.countdown-overlay.active { display: flex; }

.countdown-number {
    font-size: 9rem;
    font-weight: 900;
    background: linear-gradient(135deg, var(--accent), var(--accent2));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: countPop 0.88s ease forwards;
    line-height: 1;
}
@keyframes countPop {
    0%   { transform: scale(2.2); opacity: 0; }
    25%  { transform: scale(1);   opacity: 1; }
    75%  { transform: scale(1);   opacity: 1; }
    100% { transform: scale(0.7); opacity: 0; }
}

/* ── Game header ── */
.game-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
}
.hud-stat { display: flex; flex-direction: column; gap: 0.15rem; }
.hud-stat.center { align-items: center; }
.hud-stat.right  { align-items: flex-end; }

.hud-label {
    font-size: 0.6rem;
    letter-spacing: 2px;
    text-transform: uppercase;
    color: var(--muted);
}
.hud-value { font-size: 2rem; font-weight: 900; line-height: 1; }
.hud-value.accent { font-size: 2.6rem; color: var(--accent); }
.level-val {
    transition: color 0.3s, transform 0.3s;
    font-size: 2rem;
}

/* ── Progress bar ── */
.progress-bar { height: 3px; background: var(--surface2); border-radius: 2px; overflow: hidden; }
.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--accent), var(--accent2));
    transition: width 1s linear;
    width: 100%;
}

/* ── Question card ── */
.question-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 20px;
    padding: 2.5rem 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.2rem;
}
.question {
    font-size: 3rem;
    font-weight: 900;
    letter-spacing: -1px;
    min-height: 3.5rem;
    display: flex;
    align-items: center;
}
/* ── Answer row (input + submit button) ── */
.answer-row {
    display: flex;
    gap: 0.5rem;
    align-items: center;
    justify-content: center;
    width: 100%;
}

#answer-input {
    width: 100%;
    max-width: 150px;
    padding: 0.7rem 0.75rem;
    background: var(--surface2);
    border: 2px solid var(--border);
    border-radius: 10px;
    color: var(--text);
    font-size: 1.6rem;
    font-weight: 700;
    text-align: center;
    outline: none;
    transition: border-color 0.15s;
    -moz-appearance: textfield;
}
#answer-input::-webkit-outer-spin-button,
#answer-input::-webkit-inner-spin-button { -webkit-appearance: none; }
#answer-input:focus   { border-color: var(--accent); }
#answer-input.correct { border-color: var(--green); color: var(--green); }
#answer-input.wrong   { border-color: var(--red);   color: var(--red);   }

.btn-submit {
    width: 3.2rem;
    height: 3.2rem;
    flex-shrink: 0;
    background: var(--accent);
    border: none;
    border-radius: 10px;
    color: #fff;
    font-size: 1.3rem;
    cursor: pointer;
    transition: transform 0.1s, background 0.15s;
    display: flex;
    align-items: center;
    justify-content: center;
}
.btn-submit:active { transform: scale(0.92); }
.btn-submit.correct { background: var(--green); }
.btn-submit.wrong   { background: var(--red); }

.feedback {
    font-size: 0.9rem;
    font-weight: 700;
    height: 1.1rem;
    transition: color 0.1s;
}
.feedback.correct { color: var(--green); }
.feedback.wrong   { color: var(--red); }

/* ── Enter hint ── */
.hint {
    text-align: center;
    color: var(--muted);
    font-size: 0.75rem;
}
kbd {
    background: var(--surface2);
    border: 1px solid var(--border);
    border-radius: 4px;
    padding: 0.1rem 0.4rem;
    font-size: 0.72rem;
    font-family: inherit;
}

/* ── Floating score pop ── */
.score-pop {
    position: fixed;
    font-size: 0.95rem;
    font-weight: 900;
    color: var(--green);
    pointer-events: none;
    z-index: 50;
    animation: scoreFloat 0.85s ease forwards;
    white-space: nowrap;
}
@keyframes scoreFloat {
    0%   { opacity: 1; transform: translateY(0) scale(1.1); }
    100% { opacity: 0; transform: translateY(-48px) scale(0.85); }
}

/* ── Results ── */
.results-title {
    text-align: center;
    font-size: 2.4rem;
    font-weight: 900;
    letter-spacing: -1px;
}
.results-sub {
    text-align: center;
    color: var(--muted);
    font-size: 0.85rem;
    margin-top: -0.8rem;
}
.stats-grid {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    gap: 0.6rem;
}
.stat-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1rem 0.75rem;
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
    align-items: center;
}
.stat-label {
    font-size: 0.62rem;
    letter-spacing: 1.5px;
    text-transform: uppercase;
    color: var(--muted);
}
.stat-value { font-size: 1.7rem; font-weight: 900; line-height: 1; }
.stat-value.green { color: var(--green); }
.stat-value.red   { color: var(--red); }

.new-best {
    display: none;
    text-align: center;
    font-size: 1.1rem;
    font-weight: 900;
    letter-spacing: 4px;
    color: var(--yellow);
    animation: pulse 0.9s ease infinite;
}
@keyframes pulse {
    0%, 100% { opacity: 1; }
    50%       { opacity: 0.4; }
}

.result-actions { display: flex; flex-direction: column; gap: 0.6rem; }

/* ── Streak badge ── */
.user-left { display: flex; align-items: center; gap: 0.6rem; }
.streak-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.2rem;
    font-size: 0.82rem;
    font-weight: 700;
    color: var(--yellow);
    background: rgba(251, 191, 36, 0.12);
    border: 1px solid rgba(251, 191, 36, 0.25);
    border-radius: 20px;
    padding: 0.15rem 0.5rem;
}

/* ── Daily mode button ── */
.mode-daily { position: relative; }
.daily-badge {
    position: absolute;
    top: 0.5rem;
    right: 0.5rem;
    background: var(--green);
    color: #000;
    font-size: 0.65rem;
    font-weight: 900;
    border-radius: 50%;
    width: 1.3rem;
    height: 1.3rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* ── Menu bottom ── */
.menu-bottom-btns { display: flex; gap: 0.4rem; }

/* ── Auth modal ── */
.modal-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(8, 8, 16, 0.88);
    align-items: center;
    justify-content: center;
    z-index: 200;
    backdrop-filter: blur(8px);
    padding: 1rem;
}
.modal-overlay.active { display: flex; }

.modal {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 20px;
    padding: 2rem 1.75rem;
    width: 100%;
    max-width: 380px;
    display: flex;
    flex-direction: column;
    gap: 1.2rem;
    animation: fadeUp 0.2s ease;
}

.modal-tabs { display: flex; gap: 0.5rem; }
.modal-tab {
    flex: 1;
    padding: 0.55rem;
    background: var(--surface2);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--muted);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.15s;
}
.modal-tab.active { border-color: var(--accent); color: var(--accent); font-weight: 700; }

.modal-pane { display: none; flex-direction: column; gap: 0.75rem; }
.modal-pane.active { display: flex; }

.form-group { display: flex; flex-direction: column; gap: 0.35rem; }
.form-group label { font-size: 0.72rem; letter-spacing: 1px; color: var(--muted); }
.form-group input {
    padding: 0.65rem 0.85rem;
    background: var(--surface2);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--text);
    font-size: 1rem;          /* ≥16px prevents iOS Safari zoom on focus */
    outline: none;
    transition: border-color 0.15s;
}
.form-group input:focus { border-color: var(--accent); }

.auth-error { font-size: 0.8rem; color: var(--red); min-height: 1rem; }

/* ── User bar ── */
.user-bar {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 0.6rem 0.9rem;
}
.user-info { display: flex; align-items: center; justify-content: space-between; gap: 0.5rem; }
.user-name { font-size: 0.85rem; font-weight: 600; }
.user-name.muted { color: var(--muted); font-weight: 400; }
.btn-ghost.small { padding: 0.3rem 0.7rem; font-size: 0.75rem; }

/* ── Menu bottom row ── */
.menu-bottom {
    display: flex;
    align-items: center;
    justify-content: space-between;
}
.btn-secondary {
    background: none;
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--muted);
    padding: 0.45rem 0.9rem;
    font-size: 0.8rem;
    cursor: pointer;
    transition: all 0.15s;
}
.btn-secondary:hover { border-color: var(--accent); color: var(--accent); }

/* ── Save status ── */
.save-status { text-align: center; font-size: 0.8rem; min-height: 1rem; }

/* ── Leaderboard screen ── */
.lb-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
}
.lb-title { font-size: 1.4rem; font-weight: 900; }

.lb-list {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    max-height: 55vh;
    overflow-y: auto;
}
.lb-empty { text-align: center; color: var(--muted); font-size: 0.9rem; padding: 2rem 0; }

.lb-row {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 0.7rem 0.9rem;
}
.lb-row-me { border-color: var(--accent); background: rgba(124, 109, 250, 0.08); }

.lb-rank { font-size: 1.1rem; min-width: 2rem; text-align: center; }
.lb-name { flex: 1; font-weight: 600; font-size: 0.9rem; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.lb-scores { display: flex; flex-direction: column; align-items: flex-end; gap: 0.1rem; }
.lb-primary { font-size: 1rem; font-weight: 900; }
.lb-secondary { font-size: 0.7rem; color: var(--muted); }

/* ── Utility ── */
.hidden { display: none !important; }

/* ── Duel button ── */
.btn-duel {
    width: 100%;
    padding: 0.85rem;
    background: linear-gradient(135deg, #fa6d8f, #f5534a);
    border: none;
    border-radius: 12px;
    color: #fff;
    font-size: 1rem;
    font-weight: 800;
    letter-spacing: 2px;
    cursor: pointer;
    box-shadow: 0 4px 24px rgba(250, 109, 143, 0.3);
    transition: transform 0.15s, box-shadow 0.15s;
}
.btn-duel:hover  { transform: translateY(-2px); box-shadow: 0 6px 30px rgba(250, 109, 143, 0.45); }
.btn-duel:active { transform: translateY(0); }

/* ── Duel screen phases ── */
.duel-phase {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.2rem;
    width: 100%;
    animation: fadeUp 0.2s ease;
}

/* Searching phase */
.duel-sword       { font-size: 3.5rem; }
.duel-search-title { font-size: 1.5rem; font-weight: 900; }
.duel-search-sub  { color: var(--muted); font-size: 0.85rem; }

.duel-dots { display: flex; gap: 0.4rem; }
.duel-dots span {
    width: 8px; height: 8px;
    background: var(--accent);
    border-radius: 50%;
    animation: dotBounce 1.2s ease-in-out infinite;
}
.duel-dots span:nth-child(2) { animation-delay: 0.2s; }
.duel-dots span:nth-child(3) { animation-delay: 0.4s; }
@keyframes dotBounce {
    0%, 80%, 100% { transform: scale(0.6); opacity: 0.4; }
    40%           { transform: scale(1.1); opacity: 1; }
}

/* Matched countdown sub-phase */
.duel-found-label { font-size: 0.75rem; letter-spacing: 3px; text-transform: uppercase; color: var(--muted); }
.duel-opp-found   { font-size: 1.4rem; font-weight: 900; color: var(--accent2); }
.duel-countdown-big {
    font-size: 7rem;
    font-weight: 900;
    line-height: 1;
    background: linear-gradient(135deg, var(--accent), var(--accent2));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Active duel phase */
.duel-scores {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 1rem 1.2rem;
}
.duel-pscore {
    display: flex;
    flex-direction: column;
    gap: 0.2rem;
}
.duel-pscore.right { align-items: flex-end; }
.duel-pname   { font-size: 0.72rem; letter-spacing: 1px; color: var(--muted); text-transform: uppercase; }
.duel-pts     { font-size: 2rem; font-weight: 900; line-height: 1; transition: color 0.3s; }
.duel-correct { font-size: 0.72rem; color: var(--green); }

.duel-center { display: flex; flex-direction: column; align-items: center; gap: 0.2rem; }
.duel-vs     { font-size: 0.65rem; letter-spacing: 3px; color: var(--muted); }
.duel-timer  { font-size: 2rem; font-weight: 900; line-height: 1; transition: color 0.3s; }

/* Result phase */
.duel-result-icon  { font-size: 4rem; }
.duel-result-title { font-size: 2.4rem; font-weight: 900; letter-spacing: -1px; }
.duel-result-scores {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1.5rem;
    width: 100%;
}
.duel-result-player { display: flex; flex-direction: column; align-items: center; gap: 0.3rem; }
.duel-result-name   { font-size: 0.8rem; color: var(--muted); }
.duel-result-pts    { font-size: 2.2rem; font-weight: 900; }

/* Duel input — same as game input */
#duel-input {
    width: 100%;
    max-width: 150px;
    padding: 0.7rem 0.75rem;
    background: var(--surface2);
    border: 2px solid var(--border);
    border-radius: 10px;
    color: var(--text);
    font-size: 1.6rem;
    font-weight: 700;
    text-align: center;
    outline: none;
    transition: border-color 0.15s;
    -moz-appearance: textfield;
}
#duel-input::-webkit-outer-spin-button,
#duel-input::-webkit-inner-spin-button { -webkit-appearance: none; }
#duel-input:focus   { border-color: var(--accent); }
#duel-input.correct { border-color: var(--green); color: var(--green); }
#duel-input.wrong   { border-color: var(--red);   color: var(--red); }

/* ── Rank badges ── */
.rank-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.15rem;
    font-size: 0.72rem;
    font-weight: 700;
    border-radius: 20px;
    padding: 0.12rem 0.45rem;
    border: 1px solid;
    white-space: nowrap;
}
.rank-bronze { color: #cd7f32; background: rgba(205,127,50,0.12); border-color: rgba(205,127,50,0.35); }
.rank-silver { color: #b8b8b8; background: rgba(192,192,192,0.12); border-color: rgba(192,192,192,0.35); }
.rank-gold   { color: #ffd700; background: rgba(255,215,0,0.12);   border-color: rgba(255,215,0,0.4);   }

/* ── Rank-up overlay ── */
.rankup-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(8, 8, 16, 0.88);
    align-items: center;
    justify-content: center;
    z-index: 300;
    backdrop-filter: blur(10px);
}
.rankup-overlay.active { display: flex; }
.rankup-content {
    text-align: center;
    animation: rankUpPop 0.55s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
}
.rankup-icon  { font-size: 6rem; line-height: 1; }
.rankup-title {
    font-size: 0.85rem;
    font-weight: 900;
    letter-spacing: 6px;
    color: var(--muted);
    margin-top: 0.6rem;
    text-transform: uppercase;
}
.rankup-name {
    font-size: 3rem;
    font-weight: 900;
    letter-spacing: -1px;
    background: linear-gradient(135deg, var(--accent), var(--accent2));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
@keyframes rankUpPop {
    0%   { opacity: 0; transform: scale(0.3) rotate(-8deg); }
    70%  { opacity: 1; transform: scale(1.08) rotate(1deg); }
    100% { opacity: 1; transform: scale(1) rotate(0deg); }
}

/* ── History entries ── */
.history-entry {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 0.7rem 0.9rem;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}
.history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.history-mode  { font-weight: 700; font-size: 0.88rem; }
.history-score { font-size: 1rem; font-weight: 900; color: var(--accent); }
.history-meta  { font-size: 0.68rem; color: var(--muted); line-height: 1.4; }

/* ── Submit problem modal ── */
.submit-equation {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.6rem;
    flex-wrap: wrap;
}
.submit-equation input {
    width: 5rem;
    padding: 0.55rem;
    background: var(--surface2);
    border: 2px solid var(--border);
    border-radius: 8px;
    color: var(--text);
    font-size: 1.2rem;
    font-weight: 700;
    text-align: center;
    outline: none;
    font-family: inherit;
    -moz-appearance: textfield;
}
.submit-equation input::-webkit-outer-spin-button,
.submit-equation input::-webkit-inner-spin-button { -webkit-appearance: none; }
.submit-equation input:focus { border-color: var(--accent); }
.submit-op      { font-size: 1.2rem; font-weight: 900; color: var(--muted); }
.submit-preview { font-size: 1.1rem; font-weight: 700; color: var(--accent); min-width: 4rem; }

/* ── Responsive ── */
/* ── Mobile base (all phones) ── */
@media (max-width: 440px) {
    .screen           { padding: 1.25rem 1rem; gap: 0.8rem; }
    .logo h1          { font-size: 2.6rem; }
    .logo p           { font-size: 0.7rem; }
    .question         { font-size: 2.4rem; }
    .stats-grid       { grid-template-columns: 1fr 1fr; }
    .question-card    { padding: 1.75rem 1.5rem; gap: 1rem; }
    .mode-btn         { padding: 0.65rem 0.75rem; }
    .mode-desc        { font-size: 0.63rem; }
    .theme-dot        { width: 2.4rem; height: 2.4rem; font-size: 1rem; }
    .duel-scores      { padding: 0.75rem 0.9rem; }
    .duel-pts         { font-size: 1.6rem; }
    .duel-timer       { font-size: 1.6rem; }
    .hud-value        { font-size: 1.7rem; }
    .hud-value.accent { font-size: 2.2rem; }
}

/* ── Smaller phones (iPhone SE 2nd gen, iPhone 8 — 375px) ── */
@media (max-width: 390px) {
    .screen  { padding: 1rem 0.85rem; gap: 0.7rem; }
    .logo h1 { font-size: 2.2rem; letter-spacing: -2px; }
    .logo p  { display: none; }     /* hide tagline, save vertical space */
    .settings-row { gap: 0.5rem; }
    .pill-btn     { font-size: 0.9rem; }
    .mode-name    { font-size: 0.82rem; }
    .mode-desc    { font-size: 0.6rem; }
    .btn-primary  { padding: 0.85rem; }
    .btn-duel     { padding: 0.85rem 0.9rem; }
    .menu-bottom  { flex-direction: column; gap: 0.5rem; align-items: center; }
    .menu-bottom-btns { justify-content: center; }
    .best-label   { text-align: center; }
}

/* ── Tiny phones (iPhone SE 1st gen — 320px) ── */
@media (max-width: 340px) {
    .screen       { padding: 0.85rem 0.75rem; gap: 0.6rem; }
    .logo h1      { font-size: 2rem; }
    .settings-row { flex-direction: column; }  /* stack difficulty + time */
    .modes        { gap: 0.3rem; }
    .mode-btn     { padding: 0.55rem 0.65rem; }
    .hud-value    { font-size: 1.5rem; }
    .hud-value.accent { font-size: 1.9rem; }
    .question     { font-size: 2rem; }
    .question-card { padding: 1.5rem 1.25rem; }
    .stats-grid   { grid-template-columns: 1fr; }   /* one column on tiny screen */
}

/* ── Short screens (landscape mobile) ── */
@media (max-height: 650px) {
    .screen    { gap: 0.6rem; padding-top: 0.75rem; padding-bottom: 0.75rem; }
    .logo      { margin-bottom: 0; }
    .logo p    { display: none; }
    .mode-btn  { padding: 0.5rem 0.75rem; }
}

/* ── Theme picker ── */
.theme-picker {
    display: flex;
    gap: 0.5rem;
    justify-content: center;
}
.theme-dot {
    width: 2rem;
    height: 2rem;
    border-radius: 50%;
    border: 2px solid var(--border);
    background: var(--surface);
    cursor: pointer;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: border-color 0.15s, transform 0.15s, box-shadow 0.15s;
}
.theme-dot:hover  { transform: scale(1.2); border-color: var(--accent); }
.theme-dot.active { border-color: var(--accent); box-shadow: 0 0 8px rgba(124,109,250,0.5); }

/* ─────────────────────────────────────────────
   THEMES
   All themes keep dark backgrounds for readability.
   Override --accent / --accent2 + background.
───────────────────────────────────────────── */

/* ── ☁️ Pixel Sky ── */
body.theme-clouds {
    --accent:  #5ba8ff;
    --accent2: #a78bfa;
    background-color: #050d1c;
    background-image: radial-gradient(ellipse 70% 40% at 50% -10%, rgba(91,168,255,0.07), transparent);
}

/* ── 🌿 Meadow ── */
body.theme-meadow {
    --accent:  #34d399;
    --accent2: #86efac;
    --muted:   #3a6b4a;
    background-color: #030b05;
    background-image:
        radial-gradient(ellipse 100% 30% at 50% 100%, rgba(52,211,153,0.08), transparent),
        radial-gradient(ellipse 80%  50% at 50%   0%, rgba(5,25,10,0.6),    transparent);
}

/* ── 🌆 Synthwave ── */
body.theme-synthwave {
    --accent:  #f72585;
    --accent2: #4cc9f0;
    --muted:   #6b2255;
    background-color: #07000f;
    background-image:
        radial-gradient(ellipse 70% 30% at 50%  -5%, rgba(76,201,240,0.08),  transparent),
        radial-gradient(ellipse 90% 30% at 50% 110%, rgba(247,37,133,0.12), transparent);
}

/* ── ✨ Deep Space ── */
body.theme-space {
    --accent:  #818cf8;
    --accent2: #38bdf8;
    background-color: #020207;
    background-image:
        radial-gradient(ellipse 55% 40% at 75% 25%, rgba(124,109,250,0.06), transparent),
        radial-gradient(ellipse 40% 35% at 20% 65%, rgba(56,189,248,0.05),  transparent);
}