:root {
    --bg-color: #f8f9fa;
    --card-bg: #ffffff;
    --text-color: #1d1d1f;
    --accent-color: #007aff;
    --accent-hover: #0062cc;
    --border-color: #d2d2d7;
    --secondary-text: #86868b;
    --success-color: #34c759;
    --error-color: #ff3b30;
    --shadow: 0 4px 24px rgba(0,0,0,0.06);
    --radius: 20px;
    --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

[data-theme="dark"] {
    --bg-color: #000000;
    --card-bg: #1c1c1e;
    --text-color: #f5f5f7;
    --border-color: #38383a;
    --secondary-text: #86868b;
    --shadow: 0 4px 24px rgba(0,0,0,0.4);
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    transition: background-color 0.3s ease, color 0.3s ease;
}

body {
    font-family: var(--font-family);
    background-color: var(--bg-color);
    color: var(--text-color);
    min-height: 100vh;
    padding: 20px;
    -webkit-font-smoothing: antialiased;
}

.app-container {
    display: flex;
    justify-content: center;
    align-items: flex-start;
    gap: 20px;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.card {
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    width: 100%;
    max-width: 500px;
    padding: 30px;
    position: relative;
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    overflow: hidden;
    flex-shrink: 0;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
}

h1 {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 24px;
    text-align: center;
}

button {
    border: none;
    border-radius: 12px;
    padding: 14px 20px;
    font-size: 16px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: inherit;
}

button:active {
    transform: scale(0.98);
}

.btn-primary {
    background-color: var(--accent-color);
    color: white;
    width: 100%;
    margin-bottom: 12px;
    box-shadow: 0 4px 12px rgba(0,122,255,0.2);
}

.btn-send {
    background-color: var(--accent-color); /* Blue */
    box-shadow: 0 4px 12px rgba(0,122,255,0.2);
}

.btn-receive {
    background-color: var(--success-color); /* Green */
    box-shadow: 0 4px 12px rgba(52, 199, 89, 0.2);
}

.btn-receive:hover {
    background-color: #248a3d;
}

.btn-primary:hover {
    background-color: var(--accent-hover);
}

.btn-secondary {
    background-color: transparent;
    color: var(--accent-color);
    border: 1px solid var(--accent-color);
    width: 100%;
    margin-top: 10px;
}

select {
    background: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-color);
    padding: 6px 12px;
    border-radius: 8px;
    font-size: 14px;
    outline: none;
    cursor: pointer;
}

#themeToggle, #chatToggleBtn {
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 36px;
    height: 36px;
    padding: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    cursor: pointer;
    color: var(--text-color);
}

#chatToggleBtn:hover, #themeToggle:hover {
    background-color: rgba(128,128,128,0.1);
}

.code-section {
    background: rgba(128,128,128,0.05);
    padding: 20px;
    border-radius: 16px;
    margin-bottom: 20px;
    text-align: center;
}

textarea {
    width: 100%;
    height: 80px;
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    color: var(--text-color);
    border-radius: 10px;
    padding: 10px;
    font-family: monospace;
    font-size: 12px;
    resize: none;
    margin-bottom: 10px;
}

input {
    width: 100%;
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    color: var(--text-color);
    border-radius: 10px;
    padding: 12px;
    margin-bottom: 10px;
    font-size: 14px;
    outline: none;
}

input:focus, textarea:focus {
    border-color: var(--accent-color);
}

canvas, #qrScanner {
    max-width: 100%;
    border-radius: 12px;
    margin: 10px auto;
    display: block;
}

#qrSenderCanvas, #qrAnswerCanvas {
    background-color: white; /* QR always readable */
    padding: 10px;
}

progress {
    appearance: none;
    -webkit-appearance: none;
    width: 100%;
    height: 8px;
    border-radius: 4px;
    margin: 20px 0;
}

/* Chat Styles - Clean & Distinct */
.chat-container {
    width: 350px;
    height: 600px;
    background: var(--bg-color); /* Restored to app background */
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    border: 1px solid var(--border-color);
    transition: all 0.4s cubic-bezier(0.19, 1, 0.22, 1);
    opacity: 1;
    margin-left: 0;
    position: relative;
}

[data-theme="dark"] .chat-container {
    background: var(--bg-color);
}

.chat-container.collapsed {
    width: 0;
    opacity: 0;
    border: 0;
    padding: 0;
    margin: 0;
    pointer-events: none;
}

.chat-container.hidden {
    display: none;
}

@media (max-width: 850px) {
    .app-container {
        flex-direction: column;
        align-items: center;
    }

    .chat-container {
        width: 100%;
        max-width: 500px;
        margin-left: 0;
    }

    .chat-container.collapsed {
        width: 100%;
        height: 0;
        opacity: 0;
    }
}

.chat-header {
    padding: 10px 16px;
    background: rgba(128, 128, 128, 0.05);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    font-weight: 600;
    font-size: 16px;
    color: var(--text-color);
    height: 60px;
    flex-shrink: 0;
}

[data-theme="dark"] .chat-header {
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-color);
    border-bottom: 1px solid var(--border-color);
}

.chat-body {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    position: relative;
    background-color: var(--card-bg); /* Clean card background */
}

.chat-history {
    flex: 1;
    overflow-y: auto;
    padding: 15px;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.chat-message-wrapper {
    display: flex;
    flex-direction: column;
    max-width: 80%;
    margin-bottom: 16px;
}

.chat-message-wrapper.sent {
    align-self: flex-end;
    align-items: flex-end;
}

.chat-message-wrapper.received {
    align-self: flex-start;
    align-items: flex-start;
}

.chat-message-label {
    font-size: 13px;
    font-weight: bold;
    margin-bottom: 6px;
    margin-left: 4px;
    margin-right: 4px;
    opacity: 0.9;
}

/* Distinct label colors */
.chat-message-wrapper.sent .chat-message-label {
    color: var(--accent-color);
    text-align: right;
}

.chat-message-wrapper.received .chat-message-label {
    color: var(--secondary-text);
    text-align: left;
}

[data-theme="dark"] .chat-message-wrapper.sent .chat-message-label {
    color: #4da3ff;
}

[data-theme="dark"] .chat-message-wrapper.received .chat-message-label {
    color: #98989d;
}

.chat-message {
    padding: 10px 16px;
    border-radius: 18px;
    font-size: 15px;
    line-height: 1.4;
    color: var(--text-color);
    position: relative;
    box-shadow: 0 1px 2px rgba(0,0,0,0.1);
    word-wrap: break-word;
    display: flex;
    flex-wrap: wrap;
    font-family: var(--font-family);
    margin-bottom: 4px;
    max-width: 100%;
    transition: transform 0.2s ease;
}

.chat-message:hover {
    transform: scale(1.01);
}

[data-theme="dark"] .chat-message {
    color: white;
    box-shadow: 0 1px 2px rgba(0,0,0,0.3);
}

/* Sent messages: Blue/Accent bubble */
.chat-message.sent {
    background-color: var(--accent-color);
    color: white;
    border-bottom-right-radius: 4px; /* Subtle visual cue for flow */
}

[data-theme="dark"] .chat-message.sent {
    background-color: var(--accent-color);
    color: white;
}

/* Received messages: Grey bubble */
.chat-message.received {
    background-color: #e9e9eb; /* iOS light gray */
    color: black;
    border-bottom-left-radius: 4px;
}

[data-theme="dark"] .chat-message.received {
    background-color: #3a3a3c;
    color: white;
}

.message-content {
    width: 100%;
}

/* Remove Meta/Time styles as requested */
.message-meta, .message-time, .message-status {
    display: none;
}

.chat-input-area {
    padding: 12px;
    background: var(--card-bg);
    border-top: 1px solid var(--border-color);
    display: flex;
    gap: 10px;
    align-items: center;
    min-height: 60px;
}

[data-theme="dark"] .chat-input-area {
    background: var(--card-bg);
    border-color: var(--border-color);
}

.chat-input-area input {
    margin-bottom: 0;
    border-radius: 20px;
    padding: 10px 15px;
    border: 1px solid var(--border-color);
    background: rgba(128,128,128,0.05);
    font-size: 14px;
    flex: 1;
}

[data-theme="dark"] .chat-input-area input {
    background: rgba(255,255,255,0.05);
    color: white;
    border-color: var(--border-color);
}

.chat-input-area input:focus {
    background: var(--card-bg);
    border-color: var(--accent-color);
}

[data-theme="dark"] .chat-input-area input:focus {
    background: #000;
}

.chat-input-area button {
    width: 36px;
    height: 36px;
    padding: 0;
    border-radius: 50%;
    margin-bottom: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--accent-color);
    color: white;
    flex-shrink: 0;
    font-size: 16px;
    border: none;
    transition: transform 0.2s;
}

[data-theme="dark"] .chat-input-area button {
    color: white;
}

.chat-input-area button:hover {
    background-color: var(--accent-hover);
    transform: scale(1.05);
}

.floating-chat-btn {
    display: none !important;
    /*
    position: fixed;
    bottom: 20px;
    right: 20px;
    width: 60px;
    height: 60px;
    border-radius: 30px;
    background-color: var(--accent-color);
    color: white;
    font-size: 24px;
    box-shadow: 0 4px 12px rgba(0, 122, 255, 0.3);
    z-index: 999;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: transform 0.2s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    */
}

.floating-chat-btn:hover {
    transform: scale(1.1);
}

.floating-chat-btn.hidden {
    display: none;
}

.notification-badge {
    position: absolute;
    top: -5px;
    right: -5px;
    background-color: var(--error-color);
    color: white;
    font-size: 12px;
    font-weight: bold;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 2px solid var(--bg-color);
}

progress::-webkit-progress-bar {
    background-color: var(--border-color);
    border-radius: 4px;
}

progress::-webkit-progress-value {
    background-color: var(--success-color);
    border-radius: 4px;
    transition: width 0.3s ease;
}

.stats-text {
    font-size: 13px;
    color: var(--secondary-text);
    text-align: center;
    margin-top: -15px;
    margin-bottom: 15px;
    font-variant-numeric: tabular-nums;
}

.warning-msg.success {
    background-color: rgba(52, 199, 89, 0.1);
    color: var(--success-color);
    border-color: rgba(52, 199, 89, 0.2);
}

.status-msg {
    text-align: center;
    font-size: 14px;
    color: var(--secondary-text);
    margin-top: 10px;
    min-height: 20px;
}

.back-btn {
    background: none;
    border: none;
    color: var(--secondary-text);
    font-size: 14px;
    margin-bottom: 15px;
    padding: 0;
    width: auto;
    display: inline-flex;
    align-items: center;
}

.back-btn:hover {
    color: var(--text-color);
    background: none;
}

#fileInput {
    display: none;
}

.upload-zone {
    border: 2px dashed var(--border-color);
    border-radius: var(--radius);
    padding: 40px 20px;
    text-align: center;
    background: rgba(128,128,128,0.02);
    transition: all 0.3s ease;
    margin-bottom: 20px;
}

.upload-zone:hover, .upload-zone.dragover {
    border-color: var(--accent-color);
    background: rgba(0,122,255,0.05);
}

.upload-icon {
    font-size: 48px;
    margin-bottom: 15px;
    opacity: 0.5;
}

.upload-text {
    color: var(--secondary-text);
    margin-bottom: 10px;
    font-size: 14px;
}

.upload-btn {
    display: inline-block;
    width: auto !important;
    min-width: 200px;
    margin-top: 10px;
    margin-bottom: 10px;
}

#fileInfo {
    font-weight: 500;
    color: var(--text-color);
}

#qrSenderContainer {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 20px auto;
    background: white;
    padding: 15px;
    border-radius: 12px;
    width: fit-content;
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
}

#qrSenderContainer img, #qrSenderContainer canvas {
    display: block;
}

.warning-msg {
    background-color: rgba(255, 59, 48, 0.1);
    color: var(--error-color);
    padding: 15px;
    border-radius: 12px;
    font-size: 13px;
    margin-top: 20px;
    line-height: 1.4;
    border: 1px solid rgba(255, 59, 48, 0.2);
}

#downloadLink {
    display: block;
    text-align: center;
    background: var(--success-color);
    color: white;
    padding: 14px;
    border-radius: 12px;
    text-decoration: none;
    font-weight: 500;
    margin-top: 15px;
    box-shadow: 0 4px 12px rgba(52, 199, 89, 0.3);
}

.hidden { display: none !important; }

/* Loading spinner */
.spinner {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 2px solid rgba(128,128,128,0.2);
    border-radius: 50%;
    border-top-color: var(--accent-color);
    animation: spin 1s ease-in-out infinite;
    margin-right: 8px;
    vertical-align: middle;
}
@keyframes spin { to { transform: rotate(360deg); } }

@keyframes pulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.2); }
    100% { transform: scale(1); }
}

.warning-msg.success {
    background-color: rgba(52, 199, 89, 0.1);
    color: var(--success-color);
    border-color: rgba(52, 199, 89, 0.2);
}