:root {
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-primary: #0f172a;
    --text-secondary: #334155;
    --accent-blue: #0369a1;
    --accent-purple: #7e22ce;
    --accent-green: #15803d;
    --accent-red: #b91c1c;
    --border-color: #94a3b8;
    --input-bg: #f1f5f9;
    --font-heading: 'Inter', system-ui, sans-serif;
    --font-body: 'Inter', system-ui, sans-serif;
}

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: var(--font-body);
    margin: 0;
    padding: 0;
    line-height: 1.6;
}


header {
    text-align: center;
    padding: 2rem 1rem;
    /* Reduced padding */
    background: linear-gradient(to bottom, var(--card-bg), var(--bg-color));
    /* Removed border */
}

h1 {
    font-size: 1.8rem;
    /* Reduced from 2.5rem */
    margin-bottom: 0.5rem;
    background: linear-gradient(to right, var(--accent-blue), var(--accent-purple));
    background-clip: text;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

h2 {
    color: var(--accent-blue);
    margin-top: 0;
    /* Removed border-bottom */
}

main {
    max-width: 1000px;
    margin: 0 auto;
    padding: 2rem;
}

.interactive-panel {
    background-color: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 2rem;
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

.description {
    color: var(--text-secondary);
    margin-bottom: 2rem;
    font-size: 1.1rem;
}

.explanation-block {
    background-color: var(--input-bg);
    border-left: 4px solid var(--accent-blue);
    padding: 1.5rem;
    border-radius: 0 8px 8px 0;
    margin-bottom: 2rem;
}

.explanation-block h3 {
    margin-top: 0;
    color: var(--accent-blue);
    font-size: 1.2rem;
    margin-bottom: 1rem;
}

.step-list {
    margin: 0;
    padding-left: 1.5rem;
}

.step-list li {
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.step-list li strong {
    color: var(--accent-purple);
}

.simulation-container {
    padding: 1rem;
    background: var(--input-bg);
    border-radius: 8px;
    border: 1px solid var(--border-color);
}

/* Common Controls */
button {
    background-color: var(--accent-blue);
    color: #ffffff;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: 6px;
    font-weight: 600;
    cursor: pointer;
    transition: filter 0.2s;
}

button:hover {
    filter: brightness(1.1);
}

button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    filter: grayscale(1);
}

.next-btn {
    /* Primary Action */
    background-color: var(--accent-blue);
    color: white;
}

.back-btn {
    background: transparent;
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
    margin-right: 0.5rem;
}

.back-btn:hover {
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-primary);
    filter: none;
}

.restart-btn {
    background: transparent;
    color: var(--accent-red);
    border: 1px solid var(--accent-red);
    margin-right: 0.5rem;
}

.restart-btn:hover {
    background: rgba(239, 68, 68, 0.1);
    filter: none;
}

input[type="text"],
input[type="number"] {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.5rem;
    border-radius: 4px;
}

.controls-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    gap: 1rem;
}

.spacer {
    flex-grow: 1;
}

.secondary-btn {
    background-color: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-primary);
}

/* Toggle Switch */
.toggle-switch {
    display: flex;
    align-items: center;
    cursor: pointer;
    position: relative;
    user-select: none;
}

.toggle-switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider {
    position: relative;
    display: inline-block;
    width: 48px;
    height: 24px;
    background-color: var(--text-secondary);
    border-radius: 24px;
    transition: .4s;
    margin-right: 10px;
}

.slider:before {
    position: absolute;
    content: "";
    height: 18px;
    width: 18px;
    left: 3px;
    bottom: 3px;
    background-color: white;
    border-radius: 50%;
    transition: .4s;
}

input:checked+.slider {
    background-color: var(--accent-red);
    /* Red for Danger/Eve */
}

input:checked+.slider:before {
    transform: translateX(24px);
}

.label-text {
    font-weight: 600;
}

/* Caesar Cipher Specific Styles */
.caesar-container {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.input-group label {
    font-weight: 600;
    color: var(--accent-blue);
}

.output-box {
    background: var(--card-bg);
    padding: 1rem;
    border-radius: 6px;
    font-family: monospace;
    font-size: 1.2rem;
    border: 1px solid var(--border-color);
    min-height: 1.5em;
    word-break: break-all;
}

.demonstration {
    text-align: center;
    color: var(--text-secondary);
}

.interceptor-box {
    margin-top: 1rem;
    background: rgba(220, 38, 38, 0.1);
    /* Red tint matched to accent-red */
    border: 1px solid var(--accent-red);
    padding: 1rem;
    border-radius: 6px;
}

.interceptor-box h3 {
    color: var(--accent-red);
    margin-top: 0;
    font-size: 1.1rem;
}

.scrambled {
    font-family: monospace;
    font-weight: bold;
    color: var(--accent-red);
}

.note {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 0;
}

/* BB84 Simulation Styles */

.bb84-grid {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    overflow-x: auto;
    padding-bottom: 1rem;
}

.row {
    display: flex;
    align-items: center;
    gap: 0.25rem;
    height: 40px;
}

.cell {
    width: 40px;
    height: 40px;
    display: flex;
    justify-content: center;
    align-items: center;
    background: var(--card-bg);
    border-radius: 4px;
    font-family: monospace;
    font-size: 1.1rem;
    border: 1px solid var(--border-color);
    flex-shrink: 0;
}

.cell.label {
    width: 140px;
    justify-content: flex-start;
    padding-left: 0.5rem;
    background: transparent;
    border: none;
    color: var(--accent-blue);
    font-size: 0.9rem;
    font-weight: 600;
}

.cell.basis {
    color: var(--accent-purple);
    font-weight: bold;
}

.cell.photon {
    color: var(--accent-green);
    font-size: 1.4rem;
}

.cell.bit {
    font-weight: bold;
}

.cell.sift-match {
    background-color: rgba(22, 163, 74, 0.2);
    color: var(--accent-green);
    font-size: 0.7rem;
    border-color: var(--accent-green);
}

.cell.sift-discard {
    background-color: rgba(71, 85, 105, 0.1);
    color: var(--text-secondary);
    font-size: 0.7rem;
    opacity: 0.5;
}

.cell.bit-error {
    background-color: rgba(220, 38, 38, 0.2);
    color: var(--accent-red);
}

.cell.key-bit {
    border: 2px solid;
}

.cell.success-glow {
    border-color: var(--accent-green);
    box-shadow: 0 0 8px rgba(22, 163, 74, 0.3);
}

.cell.error-glow {
    border-color: var(--accent-red);
    box-shadow: 0 0 8px rgba(220, 38, 38, 0.3);
}

.cell.empty {
    background: transparent;
    border: none;
}

.eve-row .cell.basis {
    color: var(--accent-red);
}

.separator-row {
    height: 10px;
    border-bottom: 1px dashed var(--border-color);
    margin: 0.5rem 0;
}

.final-key-row {
    margin-top: 0.5rem;
}

.stats-panel {
    display: flex;
    gap: 2rem;
    margin-top: 1.5rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
    align-items: center;
}

.stat {
    display: flex;
    gap: 0.5rem;
    align-items: baseline;
}

.stat-label {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.stat-value {
    font-size: 1.2rem;
    font-weight: bold;
    color: var(--text-primary);
}

.text-danger {
    color: var(--accent-red);
}

.text-success {
    color: var(--accent-green);
}

.eve-warning {
    color: var(--accent-red);
    font-weight: bold;
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0% {
        opacity: 1;
    }

    50% {
        opacity: 0.6;
    }

    100% {
        opacity: 1;
    }
}

/* Secure Chat Integration Styles */
.secure-chat-hidden {
    opacity: 0.5;
    pointer-events: none;
    transition: opacity 0.5s;
    margin-top: 2rem;
    border-top: 1px solid var(--border-color);
    padding-top: 2rem;
}

.secure-chat-visible {
    opacity: 1;
    pointer-events: all;
}

.key-conversion-panel {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 1.5rem;
    background: rgba(2, 132, 199, 0.1);
    padding: 1.5rem;
    border-radius: 8px;
    margin-bottom: 2rem;
    border: 1px solid var(--accent-blue);
}

.conversion-step {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

.code-font {
    font-family: monospace;
    font-weight: bold;
    color: var(--accent-blue);
    font-size: 1.2rem;
}

.large-text {
    font-size: 2rem;
    color: var(--accent-green);
}

.arrow-right {
    font-size: 1.5rem;
    color: var(--text-secondary);
}

.secure-mode .output-box {
    border-color: var(--accent-green);
}

.success-box {
    background: rgba(22, 163, 74, 0.1);
    color: var(--accent-green);
}

.integrity-message {
    margin-top: 0.5rem;
    font-size: 0.9rem;
    font-weight: bold;
}

.integrity-ok {
    color: var(--accent-green);
}

/* Unified UI Styles */

.method-selector {
    text-align: center;
    margin-bottom: 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.method-buttons {
    display: inline-flex;
    justify-content: center;
    background-color: var(--input-bg);
    padding: 4px;
    border-radius: 50px;
    /* Pill shape */
    gap: 0;
    /* Segmented control needs no gap */
    margin-top: 1rem;
    border: 1px solid var(--border-color);
}

.method-btn {
    background-color: transparent;
    color: var(--text-secondary);
    border: none;
    padding: 0.6rem 1.4rem;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    border-radius: 50px;
    /* Inner pill */
    transition: all 0.2s;
    box-shadow: none;
}

.method-btn:hover {
    color: var(--text-primary);
    background-color: rgba(255, 255, 255, 0.5);
    transform: none;
    /* Remove lift on hover for this style */
}

.method-btn.active {
    background-color: white;
    color: var(--accent-blue);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

#simulation-stage {
    min-height: 200px;
    transition: all 0.3s;
}

.placeholder-text {
    text-align: center;
    font-style: italic;
    color: var(--text-secondary);
    padding: 3rem;
}

/* Step Containers */
.step-container {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
    margin-bottom: 2rem;
    transition: all 0.3s ease;
}

.step-container.pending {
    opacity: 0.4;
    filter: grayscale(100%);
    pointer-events: none;
    border-style: dashed;
}

.step-container.active {
    opacity: 1;
    pointer-events: all;
    border-color: var(--accent-blue);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    transform: scale(1.005);
    /* Subtle pop */
}

.step-container.completed {
    opacity: 0.7;
    background: var(--input-bg);
    border-color: var(--accent-green);
    filter: none;
}

.step-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 0.5rem;
}

.step-header h3 {
    margin: 0;
    font-size: 1.2rem;
    color: var(--accent-blue);
}

.step-actions {
    display: flex;
    gap: 1rem;
}

/* Hide chat initially */
.secure-chat-hidden {
    display: none;
}

.secure-chat-visible {
    display: block;
    animation: fadeIn 0.5s ease-in;
}


/* Scramble Animation */
.scrambling {
    color: var(--accent-purple);
    font-weight: normal;
    opacity: 0.7;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Final Key Summary Grid */
.summary-grid-container {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    margin-bottom: 2rem;
    overflow-x: auto;
    padding-bottom: 1rem;
}

.summary-row {
    display: flex;
    min-width: min-content;
}

.summary-row .cell {
    width: 40px;
    height: 40px;
    margin-right: 4px;
    flex-shrink: 0;
    transition: all 0.3s;
}

.summary-row .cell.label {
    width: 120px;
    font-size: 0.9rem;
    color: var(--text-secondary);
    background: transparent;
    border: none;
    text-align: right;
    padding-right: 1rem;
}

.summary-row .cell.dimmed {
    opacity: 0.2;
    transform: scale(0.8);
    filter: grayscale(100%);
}

.summary-row .cell.full-dim {
    opacity: 0.3;
    color: var(--text-secondary);
    border: 1px dashed var(--border-color);
    background: transparent;
}

.summary-row .cell.matched-basis {
    border-color: var(--accent-blue);
    background-color: rgba(3, 105, 161, 0.1);
}

.physics-note {
    background: linear-gradient(135deg, rgba(3, 105, 161, 0.1), rgba(147, 51, 234, 0.1));
    border-left: 4px solid var(--accent-blue);
    padding: 1rem;
    border-radius: 4px;
    margin: 1rem 0;
    font-size: 0.95rem;
    color: var(--text-primary);
    line-height: 1.5;
}

.physics-note strong {
    color: var(--accent-blue);
}

/* Public Channel Sifting Styles */
.public-channel-log {
    background: var(--input-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1rem;
    max-height: 300px;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 0.8rem;
    position: relative;
    scroll-behavior: smooth;
}

.eve-listener-banner {
    position: sticky;
    top: -1rem;
    margin: -1rem -1rem 0.5rem -1rem;
    background: var(--accent-red);
    color: white;
    text-align: center;
    padding: 0.5rem;
    font-weight: bold;
    font-size: 0.9rem;
    z-index: 10;
    opacity: 0.95;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.chat-message {
    display: flex;
    align-items: flex-start;
    gap: 0.8rem;
    max-width: 80%;
    animation: fadeIn 0.3s ease-up;
}

.chat-message.alice {
    align-self: flex-start;
}

.chat-message.bob {
    align-self: flex-end;
    flex-direction: row-reverse;
}

.chat-avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: 2px solid var(--border-color);
    background: var(--card-bg);
    object-fit: cover;
    flex-shrink: 0;
}

.msg-content {
    display: flex;
    flex-direction: column;
}

.chat-message.alice .msg-content {
    align-items: flex-start;
}

.chat-message.bob .msg-content {
    align-items: flex-end;
}

.msg-sender {
    font-size: 0.75rem;
    color: var(--text-secondary);
    margin-bottom: 0.2rem;
    margin-left: 0.5rem;
}

.chat-message.bob .msg-sender {
    margin-right: 0.5rem;
    margin-left: 0;
}

.msg-bubble {
    padding: 0.8rem 1rem;
    border-radius: 12px;
    font-size: 0.95rem;
    line-height: 1.4;
    position: relative;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
}

.chat-message.alice .msg-bubble {
    background: white;
    border: 1px solid var(--border-color);
    border-bottom-left-radius: 2px;
    color: var(--text-primary);
}

.chat-message.bob .msg-bubble {
    background: var(--accent-blue);
    color: white;
    border-bottom-right-radius: 2px;
}

.msg-highlight {
    font-weight: bold;
    font-family: monospace;
    font-size: 1.1em;
}

.keep-tag {
    background: rgba(255, 255, 255, 0.2);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.75em;
    font-weight: bold;
    margin-left: 0.5rem;
    text-transform: uppercase;
    vertical-align: middle;
}

.chat-message.alice .keep-tag {
    background: rgba(22, 163, 74, 0.1);
    color: var(--accent-green);
    border: 1px solid rgba(22, 163, 74, 0.2);
}

.drop-tag {
    background: rgba(0, 0, 0, 0.2);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.75em;
    font-weight: bold;
    margin-left: 0.5rem;
    vertical-align: middle;
}

.chat-message.alice .drop-tag {
    background: rgba(0, 0, 0, 0.05);
    color: var(--text-secondary);
}