/* ============================================================
   Grain-128 Cipher Walkthrough — Interactive Page-by-Page
   Dark mode • Animated reveals • Progressive content
   ============================================================ */

:root {
    --bg-deep: #0a0e1a;
    --bg-surface: #111827;
    --bg-card: rgba(17, 24, 39, 0.9);
    --bg-code: rgba(0, 0, 0, 0.45);

    --border-subtle: rgba(148, 163, 184, 0.1);
    --border-glow-cyan: rgba(56, 189, 248, 0.35);
    --border-glow-purple: rgba(168, 85, 247, 0.35);
    --border-glow-amber: rgba(245, 158, 11, 0.35);
    --border-glow-emerald: rgba(16, 185, 129, 0.35);

    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --cyan: #38bdf8;
    --purple: #a855f7;
    --amber: #f59e0b;
    --emerald: #10b981;
    --rose: #f43f5e;

    --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.4);
    --shadow-glow-cyan: 0 0 24px rgba(56, 189, 248, 0.2);
    --shadow-glow-purple: 0 0 24px rgba(168, 85, 247, 0.2);
    --shadow-glow-amber: 0 0 24px rgba(245, 158, 11, 0.2);
    --shadow-glow-emerald: 0 0 24px rgba(16, 185, 129, 0.2);

    --radius: 12px;
    --radius-sm: 6px;
    --radius-pill: 6px;

    --font-body: 'Inter', -apple-system, sans-serif;
    --font-mono: 'Fira Code', 'Cascadia Code', monospace;
    --ease: cubic-bezier(0.4, 0, 0.2, 1);
}

*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
html {
    font-size: 16px;
    scrollbar-width: thin;
    scrollbar-color: rgba(255, 255, 255, 0.15) transparent;
    scroll-behavior: smooth;
}
body {
    font-family: var(--font-body);
    background: var(--bg-deep);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
    overflow-y: auto;
    -webkit-font-smoothing: antialiased;
}

/* ============ APP LAYOUT ============ */
.app {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ============ TOP BAR ============ */
.topbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 0;
    border-bottom: 1px solid var(--border-subtle);
    flex-shrink: 0;
    gap: 12px;
}

.topbar-left {
    display: flex;
    align-items: center;
    gap: 12px;
    min-width: 0;
}

.topbar-back-link {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    border-radius: var(--radius-sm);
    font-size: 0.76rem;
    font-weight: 600;
    color: #f43f5e;
    background: rgba(244, 63, 94, 0.12);
    border: 1px solid rgba(244, 63, 94, 0.28);
    text-decoration: none;
    transition: all 0.2s var(--ease);
    white-space: nowrap;
    flex-shrink: 0;
}

.topbar-back-link:hover {
    background: rgba(244, 63, 94, 0.2);
    border-color: rgba(244, 63, 94, 0.5);
    color: #fda4af;
}

.back-text-short { display: none; }

.topbar-brand {
    display: flex;
    align-items: center;
    gap: 10px;
    min-width: 0;
}

.topbar-brand .logo { font-size: 24px; flex-shrink: 0; }
.topbar-brand h1 {
    font-size: 0.98rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--cyan), var(--purple));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.topbar-badges {
    display: flex;
    gap: 6px;
    flex-shrink: 0;
}

.tbadge {
    padding: 4px 10px;
    border-radius: 6px;
    font-size: 0.68rem;
    font-weight: 700;
    letter-spacing: 0.4px;
    text-transform: uppercase;
    border: 1px solid var(--border-subtle);
    background: var(--bg-card);
    white-space: nowrap;
}

.tbadge-cyan { color: var(--cyan); border-color: var(--border-glow-cyan); }
.tbadge-purple { color: var(--purple); border-color: var(--border-glow-purple); }

/* ============ STEP PROGRESS BAR ============ */
.progress-bar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 0;
    gap: 2px;
    flex-shrink: 0;
    border-bottom: 1px solid var(--border-subtle);
    width: 100%;
}

.prog-step {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 6px 8px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.25s var(--ease);
    position: relative;
    flex-shrink: 0;
}

.prog-step:hover { background: rgba(56, 189, 248, 0.06); }

.prog-dot {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.68rem;
    font-weight: 800;
    background: rgba(100, 116, 139, 0.2);
    color: var(--text-muted);
    transition: all 0.3s var(--ease);
    flex-shrink: 0;
}

.prog-step.active .prog-dot {
    background: linear-gradient(135deg, var(--cyan), var(--purple));
    color: #fff;
    box-shadow: 0 0 12px rgba(56, 189, 248, 0.4);
}

.prog-step.done .prog-dot {
    background: var(--emerald);
    color: #fff;
}

.prog-label {
    font-size: 0.74rem;
    font-weight: 600;
    color: var(--text-muted);
    white-space: nowrap;
    transition: color 0.25s var(--ease);
}

.prog-step.active .prog-label { color: var(--text-primary); }
.prog-step.done .prog-label { color: var(--emerald); }

.prog-connector {
    flex: 1 1 0;
    min-width: 8px;
    max-width: 32px;
    height: 2px;
    background: rgba(100, 116, 139, 0.2);
    transition: background 0.3s var(--ease);
}

.prog-connector.filled { background: var(--emerald); }

/* ============ PAGE CONTAINER ============ */
.page-container {
    flex: 1;
    padding: 24px 0 32px;
    width: 100%;
}

.page {
    display: none;
}

.page.active {
    display: block;
}

/* ============ PAGE HEADER ============ */
.page-head {
    margin-bottom: 20px;
}

.page-head h2 {
    font-size: 1.4rem;
    font-weight: 800;
    margin-bottom: 4px;
}

.page-head p {
    font-size: 0.88rem;
    color: var(--text-secondary);
}

/* ============ CARDS ============ */
.card {
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: var(--shadow-card);
    margin-bottom: 16px;
    backdrop-filter: blur(12px);
}

.info-box {
    font-size: 0.84rem;
    color: var(--text-secondary);
    padding: 12px 16px;
    background: rgba(56, 189, 248, 0.06);
    border-left: 3px solid var(--cyan);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    margin-bottom: 16px;
    line-height: 1.6;
}

.info-box strong { color: var(--cyan); }

/* ============ POPUP MODAL STYLING ============ */
.modal-overlay {
    position: fixed;
    inset: 0;
    width: 100%;
    height: 100%;
    background: rgba(10, 14, 26, 0.85);
    backdrop-filter: blur(8px);
    z-index: 1000;
    display: none;
    align-items: center;
    justify-content: center;
    padding: 16px;
}

.modal-overlay.active {
    display: flex;
    animation: fadeIn 0.3s ease-out;
}

.modal-card {
    background: var(--bg-surface);
    border: 1px solid var(--border-glow-purple);
    border-radius: var(--radius);
    max-width: 860px;
    width: 100%;
    max-height: 88vh;
    display: flex;
    flex-direction: column;
    box-shadow: 0 16px 48px rgba(0, 0, 0, 0.7);
    overflow: hidden;
}

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 18px;
    border-bottom: 1px solid var(--border-subtle);
    background: var(--bg-card);
    gap: 10px;
}

.modal-header h3 {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--purple);
}

.modal-close-btn {
    background: rgba(244, 63, 94, 0.15);
    border: 1px solid var(--rose);
    color: var(--rose);
    padding: 6px 14px;
    border-radius: var(--radius-sm);
    font-size: 0.8rem;
    font-weight: 700;
    cursor: pointer;
    transition: all 0.2s ease;
    flex-shrink: 0;
}

.modal-close-btn:hover {
    background: var(--rose);
    color: #fff;
}

.modal-body {
    padding: 18px;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
    flex: 1;
}

.modal-body::-webkit-scrollbar {
    width: 6px;
}
.modal-body::-webkit-scrollbar-track {
    background: transparent;
}
.modal-body::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.12);
    border-radius: 3px;
}



/* ============ STEP 1: INPUT ============ */
.msg-input {
    width: 100%;
    padding: 16px 20px;
    background: var(--bg-code);
    border: 2px solid var(--border-subtle);
    border-radius: var(--radius);
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 1.15rem;
    letter-spacing: 1.5px;
    outline: none;
    transition: border-color 0.3s, box-shadow 0.3s;
}

.msg-input:focus {
    border-color: var(--cyan);
    box-shadow: var(--shadow-glow-cyan);
}

.msg-input::placeholder {
    color: var(--text-muted);
    font-family: var(--font-body);
    font-size: 0.88rem;
    letter-spacing: 0;
}

.input-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 10px;
    flex-wrap: wrap;
    gap: 8px;
}

.counter {
    font-family: var(--font-mono);
    font-size: 0.78rem;
    color: var(--text-secondary);
    transition: color 0.3s;
}

.counter.full { color: var(--emerald); }

.presets {
    display: flex;
    gap: 6px;
    flex-wrap: wrap;
}

.preset {
    padding: 5px 12px;
    background: transparent;
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);
    color: var(--text-muted);
    font-size: 0.72rem;
    font-family: var(--font-mono);
    cursor: pointer;
    transition: all 0.25s var(--ease);
}

.preset:hover {
    border-color: var(--cyan);
    color: var(--cyan);
    background: rgba(56, 189, 248, 0.08);
}

/* ============ STEP 2: CHAR CARDS ============ */
.char-grid {
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    gap: 8px;
}

.char-card {
    background: var(--bg-code);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius);
    padding: 10px 6px;
    text-align: center;
    transition: all 0.3s var(--ease);
    cursor: pointer;
}

.char-card:hover {
    border-color: var(--border-glow-cyan);
    transform: translateY(-3px) scale(1.03);
    box-shadow: var(--shadow-glow-cyan);
}

.char-card .ch { font-size: 1.3rem; font-weight: 800; color: var(--cyan); font-family: var(--font-mono); }
.char-card .hex { font-size: 0.68rem; color: var(--purple); font-family: var(--font-mono); margin: 4px 0 2px; }
.char-card .bin { font-size: 0.62rem; color: var(--emerald); font-family: var(--font-mono); font-weight: 600; letter-spacing: 0.5px; word-break: break-all; }

.binary-result {
    margin-top: 16px;
    padding: 14px 16px;
    background: var(--bg-code);
    border: 1px solid var(--border-glow-emerald);
    border-radius: var(--radius);
    font-family: var(--font-mono);
    font-size: 0.68rem;
    color: var(--emerald);
    letter-spacing: 1px;
    line-height: 2;
    word-break: break-all;
}

.binary-result .label {
    display: block;
    font-family: var(--font-body);
    font-size: 0.72rem;
    color: var(--text-muted);
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 6px;
}

/* ============ STEP 3: REGISTERS ============ */
.reg-block {
    padding: 18px;
    background: var(--bg-code);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius);
    margin-bottom: 12px;
}

.reg-title {
    font-weight: 700;
    font-size: 0.92rem;
    margin-bottom: 6px;
}

.reg-title.lfsr { color: var(--cyan); }
.reg-title.nfsr { color: var(--purple); }

.reg-hex {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    color: var(--text-secondary);
    background: rgba(0,0,0,0.3);
    padding: 4px 10px;
    border-radius: var(--radius-sm);
    display: inline-block;
    margin-bottom: 10px;
    word-break: break-all;
}

.bit-strip {
    display: flex;
    gap: 1px;
    flex-wrap: wrap;
    margin-bottom: 10px;
}

.pip {
    width: 6px;
    height: 16px;
    border-radius: 2px;
    background: rgba(100, 116, 139, 0.2);
    transition: all 0.15s;
}

.pip.on { box-shadow: 0 0 4px currentColor; }
.lfsr-strip .pip.on { background: var(--cyan); color: var(--cyan); }
.nfsr-strip .pip.on { background: var(--purple); color: var(--purple); }

.feedback-eq {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    color: var(--text-secondary);
    padding: 8px 12px;
    background: rgba(0, 0, 0, 0.2);
    border-radius: var(--radius-sm);
    line-height: 1.7;
    word-break: break-all;
}

.lfsr-eq { border-left: 3px solid var(--cyan); }
.nfsr-eq { border-left: 3px solid var(--purple); }

.explain {
    font-size: 0.84rem;
    color: var(--text-secondary);
    padding: 14px 16px;
    background: rgba(56, 189, 248, 0.04);
    border-radius: var(--radius-sm);
    margin-top: 12px;
    line-height: 1.7;
}

.explain strong { color: var(--text-primary); }

/* ============ STEP 4: KEYSTREAM & BIT SELECTOR ============ */
.bit-selector-grid {
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    gap: 8px;
    margin-top: 8px;
}

.bit-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 8px 4px;
    background: var(--bg-code);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.2s var(--ease);
    text-align: center;
    user-select: none;
}

.bit-btn:hover {
    border-color: var(--border-glow-purple);
    background: rgba(168, 85, 247, 0.08);
}

.bit-btn.active {
    border-color: var(--purple);
    background: rgba(168, 85, 247, 0.2);
    box-shadow: 0 0 10px rgba(168, 85, 247, 0.3);
}

.bit-btn-label {
    font-family: var(--font-mono);
    font-size: 0.68rem;
    color: var(--text-muted);
}

.bit-btn.active .bit-btn-label {
    color: var(--purple);
    font-weight: 700;
}

.bit-btn-val {
    font-family: var(--font-mono);
    font-size: 0.95rem;
    font-weight: 800;
    color: var(--text-primary);
    margin-top: 2px;
}

.bit-btn.active .bit-btn-val {
    color: #fff;
}

.ks-grid {
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    gap: 8px;
}

.ks-card {
    background: var(--bg-code);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius);
    padding: 10px 6px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s var(--ease);
}

.ks-card:hover, .ks-card.selected {
    border-color: var(--border-glow-purple);
    box-shadow: var(--shadow-glow-purple);
    transform: translateY(-2px);
}

.ks-card .cyc { font-size: 0.6rem; color: var(--text-muted); font-weight: 700; text-transform: uppercase; }
.ks-card .val { font-size: 1.1rem; font-weight: 800; color: var(--purple); font-family: var(--font-mono); margin: 4px 0; }
.ks-card .bits { font-size: 0.6rem; color: var(--text-secondary); font-family: var(--font-mono); letter-spacing: 0.5px; }

/* Derivation Panel */
.deriv-panel {
    background: var(--bg-card);
    border: 1px solid var(--border-glow-purple);
    border-radius: var(--radius);
    padding: 20px;
    margin-top: 16px;
    box-shadow: var(--shadow-glow-purple);
}

.deriv-panel h3 {
    font-size: 0.95rem;
    color: var(--purple);
    margin-bottom: 14px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--border-subtle);
}

.deriv-step {
    margin-bottom: 12px;
}

.deriv-label {
    font-size: 0.72rem;
    font-weight: 700;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 4px;
}

.deriv-code {
    font-family: var(--font-mono);
    font-size: 0.76rem;
    padding: 10px 14px;
    background: var(--bg-code);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    line-height: 1.7;
    word-break: break-word;
    overflow-wrap: anywhere;
    overflow-x: auto;
}

.deriv-eval {
    font-family: var(--font-mono);
    font-size: 0.78rem;
    padding: 8px 14px;
    background: rgba(168, 85, 247, 0.08);
    border-left: 3px solid var(--purple);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    color: var(--purple);
    margin-top: 6px;
    word-break: break-word;
    overflow-wrap: anywhere;
    line-height: 1.7;
}

.deriv-result {
    font-family: var(--font-mono);
    font-size: 0.92rem;
    font-weight: 700;
    padding: 12px;
    text-align: center;
    background: rgba(168, 85, 247, 0.1);
    border: 1px solid var(--border-glow-purple);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    margin-top: 6px;
    word-break: break-word;
}

.unroll-row {
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    gap: 4px;
    margin-top: 8px;
}

.unroll-cell {
    text-align: center;
    padding: 6px 2px;
    background: var(--bg-code);
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-subtle);
}

.unroll-cell .ul { font-size: 0.6rem; color: var(--text-muted); }
.unroll-cell .uv { font-size: 0.95rem; font-weight: 800; color: var(--purple); font-family: var(--font-mono); }

.ks-summary {
    padding: 14px 16px;
    background: var(--bg-code);
    border: 1px solid var(--border-glow-purple);
    border-radius: var(--radius);
    margin-top: 16px;
    text-align: center;
}

.ks-summary .ks-label {
    display: block;
    font-size: 0.7rem;
    color: var(--text-muted);
    text-transform: uppercase;
    font-weight: 700;
    letter-spacing: 0.5px;
    margin-bottom: 6px;
}

.ks-summary .ks-val {
    font-family: var(--font-mono);
    font-size: 0.82rem;
    color: var(--purple);
    font-weight: 700;
    letter-spacing: 2px;
}

/* ============ STEP 5 & 7: XOR GRID ============ */
.xor-row {
    display: grid;
    grid-template-columns: 55px 1fr 36px 1fr 36px 1fr;
    align-items: center;
    gap: 6px;
    padding: 10px 12px;
    background: var(--bg-code);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius);
    margin-bottom: 6px;
    cursor: pointer;
    transition: all 0.3s var(--ease);
}

.xor-row:hover {
    border-color: var(--border-glow-amber);
    box-shadow: 0 0 10px rgba(245, 158, 11, 0.08);
}

.xor-row.dec-row:hover {
    border-color: var(--border-glow-emerald);
    box-shadow: 0 0 10px rgba(16, 185, 129, 0.08);
}

.xor-label {
    font-size: 0.68rem;
    font-weight: 700;
    color: var(--text-muted);
    font-family: var(--font-mono);
}

.xor-op {
    font-family: var(--font-mono);
    font-size: 0.78rem;
}

.xor-op .xh { font-weight: 700; }
.xor-op .xb { font-size: 0.65rem; color: var(--text-muted); letter-spacing: 0.5px; display: block; }
.xor-op.p-op .xh { color: var(--cyan); }
.xor-op.z-op .xh { color: var(--purple); }
.xor-op.c-op .xh { color: var(--amber); }
.xor-op.d-op .xh { color: var(--emerald); }

.xor-sym { text-align: center; font-size: 1rem; color: var(--text-muted); font-weight: 800; }

/* ============ BIT XOR TABLE & WRAPPER ============ */
.table-wrap {
    width: 100%;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    margin: 14px 0;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-subtle);
    background: var(--bg-code);
}

.table-wrap::-webkit-scrollbar {
    height: 4px;
}
.table-wrap::-webkit-scrollbar-track {
    background: transparent;
}
.table-wrap::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.12);
    border-radius: 2px;
}

.bit-table {
    width: 100%;
    min-width: 480px;
    border-collapse: collapse;
}

.bit-table th {
    font-size: 0.68rem;
    color: var(--text-muted);
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.4px;
    padding: 10px 8px;
    text-align: center;
    border-bottom: 1px solid var(--border-subtle);
    background: rgba(255, 255, 255, 0.02);
}

.bit-table td {
    font-family: var(--font-mono);
    font-size: 0.88rem;
    font-weight: 700;
    text-align: center;
    padding: 9px 8px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.02);
}

.b0 { color: var(--text-muted); }
.b1 { color: var(--cyan); }
.br { color: var(--amber); }
.bd { color: var(--emerald); }
.bx { color: var(--text-muted); font-size: 0.75rem !important; font-weight: 600 !important; }

/* ============ STEP 6: CIPHERTEXT ============ */
.cipher-strip {
    font-family: var(--font-mono);
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--amber);
    letter-spacing: 3px;
    padding: 16px;
    background: var(--bg-code);
    border: 1px solid var(--border-glow-amber);
    border-radius: var(--radius-sm);
    text-align: center;
    word-break: break-all;
}

.cipher-bin {
    margin-top: 10px;
    font-family: var(--font-mono);
    font-size: 0.7rem;
    color: var(--amber);
    opacity: 0.7;
    letter-spacing: 0.5px;
    padding: 8px 12px;
    background: var(--bg-code);
    border-radius: var(--radius-sm);
    word-break: break-all;
    line-height: 1.7;
    text-align: center;
}

.compare {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: 14px;
    align-items: center;
    margin-top: 20px;
}

.cmp-box {
    padding: 16px;
    border-radius: var(--radius-sm);
    text-align: center;
}

.cmp-box.orig { background: rgba(56, 189, 248, 0.06); border: 1px solid var(--border-glow-cyan); }
.cmp-box.enc { background: rgba(245, 158, 11, 0.06); border: 1px solid var(--border-glow-amber); }

.cmp-box .cl { font-size: 0.68rem; color: var(--text-muted); font-weight: 700; text-transform: uppercase; letter-spacing: 0.5px; margin-bottom: 6px; }
.cmp-box.orig .cv { font-family: var(--font-mono); font-size: 0.95rem; font-weight: 700; color: var(--cyan); letter-spacing: 0.5px; word-break: break-all; }
.cmp-box.enc .cv { font-family: var(--font-mono); font-size: 0.95rem; font-weight: 700; color: var(--amber); letter-spacing: 0.5px; word-break: break-all; }
.cmp-arrow { font-size: 1.4rem; color: var(--text-muted); }

/* ============ STEP 7: SUCCESS ============ */
.success {
    padding: 22px;
    background: rgba(16, 185, 129, 0.08);
    border: 1px solid var(--border-glow-emerald);
    border-radius: var(--radius-sm);
    text-align: center;
    margin-top: 16px;
}

.success .si { font-size: 2.2rem; margin-bottom: 8px; }
.success .st { font-size: 1.05rem; font-weight: 800; color: var(--emerald); margin-bottom: 4px; }
.success .ss { font-size: 0.84rem; color: var(--text-secondary); }
.success .sr {
    font-family: var(--font-mono);
    font-size: 1.3rem;
    font-weight: 800;
    color: var(--emerald);
    margin-top: 10px;
    letter-spacing: 3px;
    text-shadow: 0 0 20px rgba(16, 185, 129, 0.4);
}

.proof {
    text-align: center;
    margin-top: 12px;
    padding: 12px;
    background: var(--bg-code);
    border-radius: var(--radius-sm);
    font-family: var(--font-mono);
    font-size: 0.82rem;
    color: var(--text-secondary);
}

.proof strong { color: var(--emerald); }

/* ============ PAGE NAV FOOTER ============ */
.page-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 0 8px;
    margin-top: 24px;
    border-top: 1px solid var(--border-subtle);
    gap: 12px;
}

.nav-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px 22px;
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);
    background: rgba(255, 255, 255, 0.03);
    color: var(--text-secondary);
    font-family: var(--font-body);
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.25s var(--ease);
    min-height: 42px;
    text-decoration: none;
}

.nav-btn:hover {
    border-color: var(--cyan);
    color: var(--text-primary);
    background: rgba(56, 189, 248, 0.08);
}

.nav-btn.next {
    background: linear-gradient(135deg, rgba(56, 189, 248, 0.2), rgba(168, 85, 247, 0.2));
    border-color: var(--border-glow-cyan);
    color: #fff;
    margin-left: auto;
}

.nav-btn.next:hover {
    background: linear-gradient(135deg, rgba(56, 189, 248, 0.3), rgba(168, 85, 247, 0.3));
    box-shadow: 0 0 16px rgba(56, 189, 248, 0.25);
    transform: translateY(-1px);
}

.spacer { flex: 1; }

/* ============ APP FOOTER ============ */
.app-footer {
    text-align: center;
    padding: 20px 0 24px;
    margin-top: auto;
    border-top: 1px solid var(--border-subtle);
    flex-shrink: 0;
}

.app-footer p { font-size: 0.72rem; color: var(--text-muted); }
.app-footer .team { font-size: 0.68rem; opacity: 0.6; margin-top: 3px; }

/* ============ RESPONSIVE BREAKPOINTS ============ */
@media (max-width: 860px) {
    .prog-label { display: none; }
    .prog-step { padding: 4px; }
    .prog-dot { width: 22px; height: 22px; font-size: 0.65rem; }
    .prog-connector { min-width: 4px; }
    .bit-selector-grid { grid-template-columns: repeat(4, 1fr); gap: 6px; }
    .char-grid, .ks-grid { grid-template-columns: repeat(4, 1fr); }
    .xor-row { grid-template-columns: 40px 1fr 28px 1fr 28px 1fr; font-size: 0.7rem; }
}

@media (max-width: 640px) {
    .app { padding: 0 14px; }
    .topbar-badges { display: none; }
    .card { padding: 18px 14px; border-radius: var(--radius-sm); }
    .page-head h2 { font-size: 1.15rem; }
    .page-head p { font-size: 0.8rem; }
    .compare { grid-template-columns: 1fr; gap: 10px; }
    .cmp-arrow { transform: rotate(90deg); text-align: center; padding: 4px 0; }
    .back-text-full { display: none; }
    .back-text-short { display: inline; }
}

@media (max-width: 480px) {
    .page-footer {
        flex-direction: column-reverse;
        gap: 10px;
    }
    .nav-btn {
        width: 100%;
        justify-content: center;
    }
    .bit-selector-grid {
        grid-template-columns: repeat(4, 1fr);
        gap: 5px;
    }
    .bit-btn {
        padding: 6px 2px;
    }
    .bit-btn-label {
        font-size: 0.6rem;
    }
    .bit-btn-val {
        font-size: 0.88rem;
    }
    .input-char-row {
        flex-direction: column;
        align-items: flex-start;
    }
}

@media (max-width: 340px) {
    .bit-selector-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 4px;
    }
}

/* ============ MINIMAL SUBTLE SCROLLBAR ============ */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}
::-webkit-scrollbar-track {
    background: transparent;
}
::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.12);
    border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover {
    background: rgba(255, 255, 255, 0.22);
}