:root {
    /* Dark Theme (Default) */
    --bg-main: #1a1a1a;
    --bg-sidebar: #242424;
    --bg-chat: #1f1f1f;
    --bg-item-hover: #2c2c2c;
    --text-primary: #f2f2f2;
    --text-secondary: #aaaaaa;
    --accent: #d64545;
    --accent-hover: #e65555;
    --border: #333333;
    --msg-in: #2a2a2a;
    --msg-out: #4a2b2b;
    --shadow: 0 4px 12px rgba(0,0,0,0.5);
}

[data-theme="light"] {
    --bg-main: #f0f2f5;
    --bg-sidebar: #ffffff;
    --bg-chat: #f9f9f9;
    --bg-item-hover: #f0f0f0;
    --text-primary: #1a1a1a;
    --text-secondary: #707579;
    --accent: #d64545;
    --accent-hover: #c0392b;
    --border: #e0e0e0;
    --msg-in: #ffffff;
    --msg-out: #fdeaea;
    --shadow: 0 4px 12px rgba(0,0,0,0.1);
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--bg-main);
    color: var(--text-primary);
    height: 100vh;
    overflow: hidden;
}

.app-container {
    display: flex;
    height: 100vh;
    max-width: 1600px;
    margin: 0 auto;
}

/* Sidebar */
.sidebar {
    width: 350px;
    background: var(--bg-sidebar);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    position: relative;
}

.sidebar-header {
    padding: 15px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo { display: flex; align-items: center; gap: 10px; }
.logo-icon {
    background: var(--accent);
    color: white;
    width: 32px;
    height: 32px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
}

.header-actions button {
    background: none; border: none; font-size: 1.2rem; cursor: pointer; color: var(--text-primary);
}

.search-box { padding: 10px 20px; }
.search-box input {
    width: 100%;
    padding: 10px 15px;
    border-radius: 10px;
    border: 1px solid var(--border);
    background: var(--bg-main);
    color: var(--text-primary);
    outline: none;
}

.chats-list { flex: 1; overflow-y: auto; }

.chat-item {
    display: flex;
    padding: 12px 20px;
    gap: 15px;
    cursor: pointer;
    transition: background 0.2s;
    border-bottom: 1px solid rgba(0,0,0,0.05);
}

.chat-item:hover, .chat-item.active { background: var(--bg-item-hover); }

.avatar {
    width: 50px; height: 50px; border-radius: 50%;
    background: var(--accent);
    display: flex; align-items: center; justify-content: center;
    font-weight: bold; color: white; flex-shrink: 0;
}

.chat-info { flex: 1; min-width: 0; }
.chat-info-top { display: flex; justify-content: space-between; margin-bottom: 4px; }
.chat-info h4 { font-size: 1rem; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.chat-time { font-size: 0.75rem; color: var(--text-secondary); }
.chat-preview { 
    font-size: 0.9rem; color: var(--text-secondary); 
    white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
    display: flex; justify-content: space-between;
}
.unread-badge {
    background: var(--accent); color: white;
    padding: 2px 8px; border-radius: 10px; font-size: 0.7rem;
}

/* Chat Area */
.chat-area { flex: 1; background: var(--bg-chat); display: flex; flex-direction: column; }

.empty-state {
    flex: 1; display: flex; flex-direction: column; align-items: center;
    justify-content: center; color: var(--text-secondary);
}
.empty-icon { font-size: 4rem; margin-bottom: 10px; opacity: 0.3; }

.active-chat { display: flex; flex-direction: column; height: 100%; }

.chat-header {
    padding: 10px 20px;
    background: var(--bg-sidebar);
    border-bottom: 1px solid var(--border);
    display: flex; align-items: center; justify-content: space-between;
}

.user-info { display: flex; align-items: center; gap: 12px; }
.status { font-size: 0.8rem; color: var(--accent); }

.messages-container {
    flex: 1; padding: 20px; overflow-y: auto;
    display: flex; flex-direction: column; gap: 8px;
}

.message {
    max-width: 70%; padding: 8px 12px; border-radius: 12px;
    position: relative; font-size: 0.95rem; line-height: 1.4;
    word-wrap: break-word;
}
.msg-in { align-self: flex-start; background: var(--msg-in); border-bottom-left-radius: 2px; }
.msg-out { align-self: flex-end; background: var(--msg-out); border-bottom-right-radius: 2px; }

.msg-time {
    font-size: 0.7rem; color: var(--text-secondary);
    margin-top: 4px; text-align: right; display: block;
}

/* Input Area */
.chat-input-area {
    padding: 15px 20px; background: var(--bg-sidebar);
    display: flex; gap: 15px; align-items: center;
}

#message-form { flex: 1; display: flex; gap: 10px; }
#message-input {
    flex: 1; padding: 12px 15px; border-radius: 20px;
    border: 1px solid var(--border); background: var(--bg-main);
    color: var(--text-primary); outline: none;
}

#send-btn {
    background: none; border: none; font-size: 1.5rem;
    color: var(--accent); cursor: pointer; transition: transform 0.2s;
}
#send-btn:hover { transform: scale(1.1); }

/* Modals & Menus */
.hidden { display: none !important; }
.modal {
    position: fixed; inset: 0; background: rgba(0,0,0,0.7);
    display: flex; align-items: center; justify-content: center; z-index: 100;
}
.modal-content {
    background: var(--bg-sidebar); padding: 30px; border-radius: 15px;
    width: 350px; box-shadow: var(--shadow);
}
.setting-item { margin: 20px 0; }
.setting-item input {
    width: 100%; padding: 10px; margin-top: 8px;
    background: var(--bg-main); border: 1px solid var(--border); color: var(--text-primary);
}
.modal-actions { display: flex; justify-content: flex-end; gap: 10px; }
button.btn-primary { background: var(--accent); color: white; border: none; padding: 8px 16px; border-radius: 5px; cursor: pointer;}
button.btn-secondary { background: transparent; color: var(--text-secondary); border: 1px solid var(--border); padding: 8px 16px; border-radius: 5px; cursor: pointer;}

.context-menu {
    position: fixed; background: var(--bg-sidebar); border: 1px solid var(--border);
    border-radius: 8px; box-shadow: var(--shadow); z-index: 1000; overflow: hidden;
}
.context-menu ul { list-style: none; }
.context-menu li { padding: 10px 20px; cursor: pointer; font-size: 0.9rem; }
.context-menu li:hover { background: var(--bg-item-hover); }
.context-menu li.danger { color: var(--accent); }

.fab {
    position: absolute; bottom: 20px; right: 20px;
    width: 50px; height: 50px; border-radius: 50%;
    background: var(--accent); color: white; border: none;
    font-size: 1.5rem; cursor: pointer; box-shadow: var(--shadow);
}

/* Scrollbar */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 10px; }

/* Mobile */
@media (max-width: 768px) {
    .sidebar { width: 100%; }
    .chat-area { display: none; position: fixed; inset: 0; z-index: 10; }
    .chat-area.active { display: flex; }
    .mobile-only { display: block; background: none; border: none; font-size: 1.2rem; color: var(--text-primary); margin-right: 10px;}
}
@media (min-width: 769px) { .mobile-only { display: none; } }

/* --- Added for PHP backend integration --- */
.auth-overlay { position: fixed; inset: 0; background: rgba(0,0,0,0.75); z-index: 2000; display:flex; align-items:center; justify-content:center; }
.auth-card { width: 420px; max-width: calc(100vw - 40px); background: var(--bg-sidebar); border: 1px solid var(--border); border-radius: 16px; box-shadow: var(--shadow); padding: 22px; }
.auth-card h3 { margin-bottom: 12px; }
.auth-tabs { display:flex; gap: 8px; margin-bottom: 12px; }
.auth-tabs button { flex: 1; border-radius: 10px; border: 1px solid var(--border); background: var(--bg-main); color: var(--text-primary); padding: 10px; cursor:pointer; }
.auth-tabs button.active { background: var(--bg-item-hover); border-color: var(--accent); }
.auth-card .row { margin: 10px 0; }
.auth-card label { display:block; font-size: 0.85rem; color: var(--text-secondary); margin-bottom: 6px; }
.auth-card input { width:100%; padding: 10px 12px; border-radius: 10px; border: 1px solid var(--border); background: var(--bg-main); color: var(--text-primary); outline:none; }
.auth-card .actions { display:flex; gap: 10px; justify-content:flex-end; margin-top: 12px; }
.auth-card .hint { margin-top: 10px; font-size: 0.85rem; color: var(--text-secondary); }
.auth-error { margin-top: 10px; font-size: 0.85rem; color: var(--accent); }

/* Message extras */
.message .meta { display:flex; gap: 8px; align-items:center; justify-content:flex-end; }
.message .pill { font-size: 0.7rem; border: 1px solid var(--border); border-radius: 999px; padding: 1px 6px; color: var(--text-secondary); }
.message .reply-snippet { border-left: 2px solid var(--accent); padding-left: 8px; margin-bottom: 6px; color: var(--text-secondary); font-size: 0.85rem; }
.message .attachments { margin-top: 6px; display:flex; flex-direction:column; gap: 6px; }
.message .attachment { display:flex; gap: 10px; align-items:center; padding: 8px 10px; border: 1px solid var(--border); border-radius: 10px; background: rgba(0,0,0,0.08); }
.message .attachment a { color: var(--text-primary); text-decoration:none; }
.message .attachment small { color: var(--text-secondary); }
.reactions { margin-top: 6px; display:flex; flex-wrap: wrap; gap: 6px; }
.reaction { border: 1px solid var(--border); background: var(--bg-main); padding: 2px 8px; border-radius: 999px; cursor:pointer; font-size: 0.85rem; }
.reaction.active { border-color: var(--accent); }