fix(pygal): address review feedback for line-retention-cohort

Attempt 2/3 - fixes based on AI review

Author: github-actions[bot]

plots/line-retention-cohort/implementations/pygal.py

@@ -1,4 +1,4 @@
-""" pyplots.ai
+"""pyplots.ai
 line-retention-cohort: User Retention Curve by Cohort
 Library: pygal 3.1.0 | Python 3.14.3
 Quality: 81/100 | Created: 2026-03-16
@@ -31,28 +31,37 @@
         retention.append(max(round(prev - max(drop, 0.5), 1), 5.0))
     retention_data[cohort] = retention
 
-# Style - reference line color first, then cohort colors fading from muted to vivid
+# Style - threshold line first, then cohort colors with higher minimum opacity
 colors_with_opacity = (
-    "rgba(180, 60, 60, 0.6)",
-    "rgba(48, 105, 152, 0.45)",
-    "rgba(232, 119, 93, 0.55)",
-    "rgba(80, 168, 110, 0.70)",
-    "rgba(212, 168, 67, 0.85)",
-    "rgba(139, 107, 174, 1.0)",
+    "rgba(200, 50, 50, 0.85)",
+    "rgba(48, 105, 152, 0.65)",
+    "rgba(220, 100, 70, 0.75)",
+    "rgba(60, 160, 100, 0.85)",
+    "rgba(200, 155, 50, 0.92)",
+    "rgba(130, 90, 170, 1.0)",
 )
 
 custom_style = Style(
-    background="white",
-    plot_background="white",
-    foreground="#333",
-    foreground_strong="#333",
-    foreground_subtle="#cccccc",
+    background="#fafafa",
+    plot_background="#fafafa",
+    foreground="#2a2a2a",
+    foreground_strong="#1a1a1a",
+    foreground_subtle="#d8d8d8",
     colors=colors_with_opacity,
     title_font_size=72,
     label_font_size=48,
     major_label_font_size=42,
     legend_font_size=40,
     value_font_size=36,
+    opacity=".95",
+    opacity_hover="1",
+    transition="200ms ease-in",
+    font_family="'Segoe UI', 'Helvetica Neue', Arial, sans-serif",
+    title_font_family="'Segoe UI', 'Helvetica Neue', Arial, sans-serif",
+    legend_font_family="'Segoe UI', 'Helvetica Neue', Arial, sans-serif",
+    label_font_family="'Segoe UI', 'Helvetica Neue', Arial, sans-serif",
+    major_label_font_family="'Segoe UI', 'Helvetica Neue', Arial, sans-serif",
+    value_font_family="'Segoe UI', 'Helvetica Neue', Arial, sans-serif",
 )
 
 # Plot
@@ -69,35 +78,46 @@
     show_y_guides=True,
     show_x_guides=False,
     legend_at_bottom=True,
+    legend_at_bottom_columns=3,
     truncate_legend=-1,
     range=(0, 105),
     x_label_rotation=0,
     value_formatter=lambda x: f"{x:.0f}%" if x is not None else "",
     tooltip_fancy_mode=True,
+    tooltip_border_radius=6,
     interpolate="cubic",
+    show_minor_x_labels=False,
+    y_labels=[0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100],
+    margin_top=40,
+    margin_bottom=60,
+    spacing=30,
 )
 
 chart.x_labels = [str(w) for w in weeks]
+chart.x_labels_major = ["0", "3", "6", "9", "12"]
 
-# Add reference threshold line at 20% retention
+# Add reference threshold line at 20% retention - bold and visible
 chart.add(
-    "20% Retention Threshold",
+    "\u2500\u2500 20% Retention Threshold",
     [20.0] * len(weeks),
-    stroke_style={"width": 2, "dasharray": "12, 8"},
+    stroke_style={"width": 3, "dasharray": "16, 8"},
     show_dots=False,
     dots_size=0,
 )
 
 # Add cohorts with increasing stroke width for newer cohorts
-stroke_widths = [2, 3, 4, 5, 7]
+stroke_widths = [3, 3.5, 4, 5, 7]
 dot_sizes = [4, 5, 5, 6, 8]
 cohort_list = list(cohorts.items())
 
 for i, (cohort, params) in enumerate(cohort_list):
     label = f"{cohort} (n={params['size']:,})"
     chart.add(
         label,
-        [{"value": v, "label": f"Week {w}: {v:.1f}% retained"} for w, v in zip(weeks, retention_data[cohort], strict=True)],
+        [
+            {"value": v, "label": f"Week {w}: {v:.1f}% retained"}
+            for w, v in zip(weeks, retention_data[cohort], strict=True)
+        ],
         stroke_style={"width": stroke_widths[i]},
         dots_size=dot_sizes[i],
     )