reveal the crab rave line from the middle and outwards

Instead of fading in like the texts, the line grows from the middle to
both ends with soft edges over the same second, slowing down as it
reaches its full width.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/cogs/meme.py

@@ -14,6 +14,7 @@ from discord.ext import commands
 from moviepy import ColorClip
 from moviepy import CompositeVideoClip
 from moviepy import ImageClip
+from moviepy import VideoClip
 from moviepy import VideoFileClip
 from moviepy import vfx
 from PIL import Image
@@ -455,6 +456,19 @@ class Meme(commands.Cog):
         gap = 21
         line = ColorClip(size=(line_width, line_thickness), color=(255, 255, 255)).with_position(("center", line_top))
 
+        # Reveal the line from the middle and outwards with soft edges, while the texts fade in
+        reveal_duration, soft_edge = 1.0, 60
+        distance_from_middle = np.abs(np.arange(line_width) - (line_width - 1) / 2)
+
+        def line_mask(t: float) -> np.ndarray:
+            # Ease out, so the reveal slows down as it reaches the ends
+            progress = 1 - (1 - min(t / reveal_duration, 1)) ** 3
+            half_width = progress * (line_width / 2 + soft_edge)
+            row = np.clip((half_width - distance_from_middle) / soft_edge, 0, 1)
+            return np.tile(row, (line_thickness, 1))
+
+        line = line.with_mask(VideoClip(line_mask, is_mask=True, duration=26.0))
+
         # Leave 5% of the video's width free on each side. Long texts are shrunk to fit
         max_width = int(clip.w * 0.9)
         top_part, top_baseline, _ = Meme.text_clip(top_text, 60, stroke_width=2, max_width=max_width)
@@ -466,12 +480,13 @@ class Meme(commands.Cog):
             ("center", line_top + line_thickness + gap - (bottom_baseline - bottom_cap_height))
         )
 
-        parts = [
-            part.with_start(11.0).with_duration(26.0).with_effects([vfx.CrossFadeIn(1)])
-            for part in (top_part, line, bottom_part)
-        ]
+        top_part, bottom_part = (
+            part.with_start(11.0).with_duration(26.0).with_effects([vfx.CrossFadeIn(reveal_duration)])
+            for part in (top_part, bottom_part)
+        )
+        line = line.with_start(11.0).with_duration(26.0)
 
-        video = CompositeVideoClip([clip, *parts]).with_duration(26.0)
+        video = CompositeVideoClip([clip, top_part, line, bottom_part]).with_duration(26.0)
 
         video.write_videofile(
             f"./src/assets/temp/{user_id}_crab.mp4",