:root { --vh: 1dvh; }
body { height: calc(var(--vh) * 100); overflow: hidden; position: fixed; width: 100%; }
#chat-container::-webkit-scrollbar { width: 4px; }
#chat-container::-webkit-scrollbar-thumb { background: #cbd5e1; border-radius: 10px; }
.bg-whatsapp { 
    background-color: #e5ddd5; 
    background-image: url('https://user-images.githubusercontent.com/15075759/28719144-86dc0f70-73b1-11e7-911d-60d70fcded21.png');
    background-blend-mode: overlay;
}
.input-area { padding-bottom: env(safe-area-inset-bottom); }
@media (max-width: 768px) {
    .side-panel { width: 100%; position: absolute; inset: 0; z-index: 50; transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1); }
    .chat-panel { width: 100%; position: absolute; inset: 0; z-index: 10; }
}
.user-item, #send-btn, #btn-plus { touch-action: manipulation; cursor: pointer; }
#chat-container { display: flex; flex-direction: column; height: 100%; }