* {
    box-sizing: border-box;
}

:root {
    --page-background: #eef2f7;
    --panel-background: #ffffff;
    --header-background: #172033;
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --assistant-background: #f1f5f9;
    --user-background: #2563eb;
    --user-text: #ffffff;
    --normal-text: #172033;
    --muted-text: #64748b;
    --border-color: #dbe2ea;
    --error-color: #b91c1c;
}

body {
    margin: 0;
    min-height: 100vh;
    padding: 24px;
    display: flex;
    justify-content: center;
    align-items: center;
    background: var(--page-background);
    color: var(--normal-text);
    font-family: Arial, Helvetica, sans-serif;
}

.chat-container {
    width: 100%;
    max-width: 820px;
    height: min(850px, calc(100vh - 48px));
    display: flex;
    flex-direction: column;
    overflow: hidden;
    background: var(--panel-background);
    border-radius: 18px;
    box-shadow: 0 15px 45px rgba(15, 23, 42, 0.12);
}

.chat-header {
    padding: 20px 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 20px;
    background: var(--header-background);
    color: #ffffff;
}

.chat-header h1 {
    margin: 0 0 4px;
    font-size: 22px;
}

.chat-header p {
    margin: 0;
    color: #cbd5e1;
    font-size: 14px;
}

.clear-button {
    padding: 9px 13px;
    color: #ffffff;
    background: transparent;
    border: 1px solid #64748b;
    border-radius: 8px;
    cursor: pointer;
}

.clear-button:hover {
    background: rgba(255, 255, 255, 0.1);
}

.chat-messages {
    flex: 1;
    padding: 24px;
    overflow-y: auto;
    scroll-behavior: smooth;
}

.message {
    max-width: 78%;
    margin-bottom: 18px;
}

.message-label {
    margin-bottom: 5px;
    color: var(--muted-text);
    font-size: 12px;
    font-weight: bold;
}

.message-content {
    padding: 13px 16px;
    border-radius: 14px;
    line-height: 1.5;
    overflow-wrap: anywhere;
    white-space: pre-wrap;
}

.assistant-message {
    margin-right: auto;
}

.assistant-message .message-content {
    background: var(--assistant-background);
    border-bottom-left-radius: 4px;
}

.user-message {
    margin-left: auto;
}

.user-message .message-label {
    text-align: right;
}

.user-message .message-content {
    background: var(--user-background);
    color: var(--user-text);
    border-bottom-right-radius: 4px;
}

.error-message .message-content {
    color: var(--error-color);
    background: #fee2e2;
}

.status-message {
    min-height: 22px;
    padding: 0 24px;
    color: var(--muted-text);
    font-size: 13px;
}

.chat-form {
    padding: 16px 24px 8px;
    display: flex;
    gap: 12px;
    align-items: flex-end;
    border-top: 1px solid var(--border-color);
}

.chat-form textarea {
    flex: 1;
    min-height: 48px;
    max-height: 160px;
    padding: 13px 15px;
    resize: none;
    font: inherit;
    line-height: 1.4;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    outline: none;
}

.chat-form textarea:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.12);
}

.send-button {
    min-width: 90px;
    height: 48px;
    padding: 0 18px;
    color: #ffffff;
    background: var(--primary);
    border: none;
    border-radius: 12px;
    font-weight: bold;
    cursor: pointer;
}

.send-button:hover {
    background: var(--primary-hover);
}

.send-button:disabled,
.clear-button:disabled,
.chat-form textarea:disabled {
    cursor: not-allowed;
    opacity: 0.65;
}

.chat-hint {
    margin: 0;
    padding: 0 24px 16px;
    color: var(--muted-text);
    font-size: 12px;
}

.typing-indicator .message-content::after {
    content: "...";
    animation: typing 1.2s infinite;
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

@keyframes typing {
    0% { opacity: 0.25; }
    50% { opacity: 1; }
    100% { opacity: 0.25; }
}

@media (max-width: 600px) {
    body { padding: 0; }

    .chat-container {
        height: 100vh;
        border-radius: 0;
    }

    .chat-header,
    .chat-messages,
    .chat-form {
        padding-left: 16px;
        padding-right: 16px;
    }

    .message { max-width: 88%; }
    .send-button { min-width: 72px; }
}