[gnome-tetravex] Improve Synesthesia.

[Arnaud B. <arnaudb src gnome org>]

commit bc1e84a3921b5fd82efe76b38abc4fc1e0ccbdd9
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Wed Oct 16 13:32:07 2019 +0200

    Improve Synesthesia.

 src/theme-synesthesia.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/theme-synesthesia.vala b/src/theme-synesthesia.vala
index 470fe64..4079806 100644
--- a/src/theme-synesthesia.vala
+++ b/src/theme-synesthesia.vala
@@ -111,7 +111,7 @@ private class SynesthesiaTheme : Theme
         /* arrow */
         arrow_w = new_size * PuzzleView.gap_factor * 0.5;
         arrow_x = (new_size * PuzzleView.gap_factor - arrow_w) * 0.5;
-        arrow_half_h = arrow_w * Math.SQRT2 / 2.0;
+        arrow_half_h = arrow_w / Math.sqrt (3.0);
         neg_arrow_half_h = -arrow_half_h;
 
         /* socket and tiles */