default crossfade to 6: measured to hold the scene together

app.py

@@ -411,10 +411,15 @@ with gr.Blocks(title="LiveWan") as demo:
                                     label="Generate (seconds of video)")
                 steer_at = gr.Slider(1, 13, value=6, step=0.5,
                                      label="Swap at (seconds in)")
-                crossfade = gr.Slider(0, 12, value=0, step=1,
+                # The local UI defaults this to 0, which is right when a human is
+                # watching and can react. For a one-click demo it is the wrong
+                # default: at 0 a waterfall steered to an aurora has collapsed into
+                # blocking by 14 s, and at 8 the scene is still standing.
+                crossfade = gr.Slider(0, 12, value=6, step=1,
                                       label="Crossfade (blocks)",
-                                      info="0 swaps instantly. Blending over a few "
-                                           "blocks softens a big jump.")
+                                      info="Blending the swap over a few blocks "
+                                           "holds the scene together. 0 swaps "
+                                           "instantly, which is harsher.")
                 seed = gr.Number(value=0, precision=0, label="Seed")
                 run_btn = gr.Button("Stream", variant="primary", size="lg")