:root {
  --bg-dark:#0f0f0f; --bg-sidebar:#1a1a2e; --bg-chat:#16213e;
  --bg-input:#1e2a4a; --bg-msg-out:#0a3d62; --bg-msg-in:#2d2d44;
  --accent:#00d2ff; --accent2:#7b2ff7; --text:#e8e8e8;
  --text-dim:#888; --border:#2a2a4a; --online:#00e676; --offline:#555;
}
*{margin:0;padding:0;box-sizing:border-box}
body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;background:var(--bg-dark);color:var(--text);height:100vh;overflow:hidden}
.screen{display:none;height:100vh}.screen.active{display:flex}
#login-screen{justify-content:center;align-items:center;background:linear-gradient(135deg,#0f0f0f,#1a1a2e,#16213e)}
.login-box{text-align:center;padding:40px;border-radius:20px;background:rgba(255,255,255,.05);backdrop-filter:blur(10px);border:1px solid var(--border);width:340px}
.login-logo{font-size:64px;margin-bottom:10px}
.login-box h1{font-size:28px;background:linear-gradient(90deg,var(--accent),var(--accent2));-webkit-background-clip:text;-webkit-text-fill-color:transparent;margin-bottom:5px}
.login-subtitle{color:var(--text-dim);margin-bottom:25px;font-size:14px}
.login-box input{width:100%;padding:14px 18px;margin-bottom:12px;border:1px solid var(--border);border-radius:12px;background:var(--bg-input);color:var(--text);font-size:15px;outline:none;transition:border .3s}
.login-box input:focus{border-color:var(--accent)}
#login-btn{width:100%;padding:14px;border:none;border-radius:12px;background:linear-gradient(90deg,var(--accent),var(--accent2));color:#fff;font-size:16px;font-weight:600;cursor:pointer;transition:opacity .3s}
#login-btn:hover{opacity:.85}#login-btn:disabled{opacity:.5;cursor:not-allowed}
.status-msg{margin-top:12px;font-size:13px;color:var(--accent);min-height:20px}
.status-msg.error{color:#ff4757}
#chat-screen{flex-direction:row}
#sidebar{width:300px;background:var(--bg-sidebar);border-right:1px solid var(--border);display:flex;flex-direction:column;flex-shrink:0}
.sidebar-header{padding:16px;border-bottom:1px solid var(--border);display:flex;justify-content:space-between;align-items:center}
.sidebar-header span{font-size:14px;color:var(--accent);font-weight:600}
#logout-btn{background:none;border:none;color:var(--text-dim);font-size:18px;cursor:pointer;padding:4px 8px;border-radius:8px}
#logout-btn:hover{background:rgba(255,71,87,.2);color:#ff4757}
#contact-list{flex:1;overflow-y:auto}
.contact-item{padding:14px 16px;cursor:pointer;display:flex;align-items:center;gap:12px;border-bottom:1px solid rgba(255,255,255,.03);transition:background .2s}
.contact-item:hover{background:rgba(255,255,255,.05)}
.contact-item.active{background:rgba(0,210,255,.1);border-left:3px solid var(--accent)}
.contact-avatar{width:40px;height:40px;border-radius:50%;background:var(--accent2);display:flex;align-items:center;justify-content:center;font-size:16px;font-weight:700;color:#fff;flex-shrink:0}
.contact-info{flex:1;min-width:0}
.contact-name{font-size:15px;font-weight:500;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.contact-status-dot{width:10px;height:10px;border-radius:50%;flex-shrink:0}
.contact-status-dot.online{background:var(--online);box-shadow:0 0 6px var(--online)}
.contact-status-dot.offline{background:var(--offline)}
.sidebar-footer{padding:10px;border-top:1px solid var(--border);display:flex;gap:8px}
.sidebar-footer input{flex:1;padding:10px 12px;border:1px solid var(--border);border-radius:10px;background:var(--bg-input);color:var(--text);font-size:13px;outline:none}
.sidebar-footer button{padding:10px 14px;border:none;border-radius:10px;background:var(--accent);color:#000;font-weight:700;cursor:pointer;font-size:16px}
#chat-area{flex:1;display:flex;flex-direction:column;background:var(--bg-chat)}
#chat-header{padding:14px 20px;border-bottom:1px solid var(--border);display:flex;align-items:center;gap:12px}
#back-btn{display:none;background:none;border:none;color:var(--text);font-size:22px;cursor:pointer;padding:4px}
#chat-with{font-size:16px;font-weight:600}
#chat-status{font-size:12px;color:var(--text-dim)}
#messages{flex:1;overflow-y:auto;padding:20px;display:flex;flex-direction:column;gap:8px}
.message{max-width:70%;padding:10px 16px;border-radius:16px;font-size:14px;line-height:1.5;word-wrap:break-word;animation:fadeIn .2s ease}
.message.out{align-self:flex-end;background:var(--bg-msg-out);border-bottom-right-radius:4px}
.message.in{align-self:flex-start;background:var(--bg-msg-in);border-bottom-left-radius:4px}
.message .time{font-size:11px;color:var(--text-dim);margin-top:4px;text-align:right}
@keyframes fadeIn{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}
#chat-input-area{padding:12px 16px;border-top:1px solid var(--border);display:flex;gap:10px;background:var(--bg-sidebar)}
#msg-input{flex:1;padding:14px 18px;border:1px solid var(--border);border-radius:16px;background:var(--bg-input);color:var(--text);font-size:15px;outline:none;transition:border .3s}
#msg-input:focus{border-color:var(--accent)}
#send-btn{padding:14px 20px;border:none;border-radius:16px;background:linear-gradient(90deg,var(--accent),var(--accent2));color:#fff;font-size:18px;cursor:pointer;transition:opacity .3s}
#send-btn:hover{opacity:.85}
::-webkit-scrollbar{width:6px}::-webkit-scrollbar-track{background:transparent}::-webkit-scrollbar-thumb{background:var(--border);border-radius:3px}
@media(max-width:600px){#sidebar{width:100%;position:absolute;z-index:10}#chat-screen.chat-open #sidebar{display:none}#chat-screen.chat-open #back-btn{display:block}.message{max-width:85%}}