diff --git a/src/sounddiff/cli.py b/src/sounddiff/cli.py
index 2355aa9..ad3201b 100644
--- a/src/sounddiff/cli.py
+++ b/src/sounddiff/cli.py
@@ -20,8 +20,8 @@
 
 
 @click.command()
-@click.argument("file_a", type=click.Path(exists=True))
-@click.argument("file_b", type=click.Path(exists=True))
+@click.argument("file_a", type=click.Path(), required=False)
+@click.argument("file_b", type=click.Path(), required=False)
 @click.option(
     "--format",
     "output_format",
@@ -51,8 +51,8 @@
 )
 @click.version_option(version=__version__, prog_name="sounddiff")
 def main(
-    file_a: str,
-    file_b: str,
+    file_a: str | None,
+    file_b: str | None,
     output_format: str,
     output_path: str | None,
     verbose: bool,
@@ -65,6 +65,34 @@ def main(
     Compares FILE_A (reference) against FILE_B (comparison) and reports
     differences in loudness, spectral content, timing, and potential issues.
     """
+    console = Console()
+    
+    # No arguments provided - show help
+    if file_a is None:
+        ctx = click.get_current_context()
+        click.echo(ctx.get_help())
+        sys.exit(0)
+    
+    # Only one file provided
+    if file_b is None:
+        console.print("[red]Error:[/red] sounddiff needs two files to compare.")
+        console.print(f"[dim]Got: {file_a}[/dim]")
+        console.print("[dim]Usage: sounddiff FILE_A FILE_B[/dim]")
+        sys.exit(1)
+    
+    # Validate file_a
+    path_a = pathlib.Path(file_a)
+    if not path_a.exists():
+        console.print(f"[red]Error:[/red] File not found: [bold]{file_a}[/bold]")
+        console.print(f"[dim]Looked in: {path_a.parent.absolute()}[/dim]")
+        sys.exit(1)
+    
+    # Validate file_b
+    path_b = pathlib.Path(file_b)
+    if not path_b.exists():
+        console.print(f"[red]Error:[/red] File not found: [bold]{file_b}[/bold]")
+        console.print(f"[dim]Looked in: {path_b.parent.absolute()}[/dim]")
+        sys.exit(1)
     # Best-effort duration probe: if sf.info() fails for either file,
     # skip the progress bar and let diff() raise the proper error message.
     show_progress = False