Invert background, add a subtle shadow

src/components/thread/index.tsx

@@ -315,7 +315,7 @@ export function Thread() {
 
                 <ScrollToBottom className="absolute bottom-full left-1/2 -translate-x-1/2 mb-4 animate-in fade-in-0 zoom-in-95" />
 
-                <div className="bg-muted rounded-2xl border mx-auto mb-8 w-full max-w-4xl relative z-10">
+                <div className="bg-muted rounded-2xl border shadow-xs mx-auto mb-8 w-full max-w-4xl relative z-10">
                   <form
                     onSubmit={handleSubmit}
                     className="grid grid-rows-[1fr_auto] gap-2 max-w-4xl mx-auto"
@@ -344,7 +344,7 @@ export function Thread() {
                       ) : (
                         <Button
                           type="submit"
-                          className="transition-all"
+                          className="transition-all shadow-md"
                           disabled={isLoading || !input.trim()}
                         >
                           Send