Use 'thick_shape" for drawing outline for black-white dark case

Co-authored-by: Yvonne Fröhlich <94163266+yvonnefroehlich@users.noreply.github.com>

Author: yvonnefroehlich

pygmt/src/pygmtlogo.py

@@ -66,19 +66,17 @@ def _create_logo(  # noqa: PLR0915
             color_gmt = color_light
 
     # Define shape
-    match shape:
-        case "circle":
-            symbol = "c"  # circle
-            size_shape = r0 + r1  # radius
-            size_shape_add = r0 - r1
-            vline_y = r0
-            arrow_y = -r0
-        case "hexagon":
-            symbol = "h"  # hexagon
-            size_shape = r0 * 2  # diameter
-            size_shape_add = 0.6
-            vline_y = r0 * 0.93
-            arrow_y = -r0 * 0.93
+    match shape:
+        case "circle":
+            symbol = "c"
+            size_shape = r0 + r1
+            vline_y = r0
+            arrow_y = -r0
+        case "hexagon":
+            symbol = "h"
+            size_shape = r0 * 2
+            vline_y = r0 * 0.93
+            arrow_y = -r0 * 0.93
 
     # Define wordmark
     font = "AvantGarde-Book"
@@ -212,7 +210,7 @@ def _vline_coords(gap=0):
         fig.plot(
             x=0,
             y=0,
-            style=f"{symbol}{size_shape + size_shape_add}c",
+            style=f"{symbol}{size_shape + thick_shape}c",
             pen=f"1p,{color_dark}",
             perspective=True,
             no_clip=True,