implement tunnels

bin/config/visuals.toml

@@ -72,6 +72,16 @@ fill    = "#7a7a5a"
 outline = "#9a9a7a"
 glyph   = ""
 
+[buildings.tunnel_entry]
+fill    = "#4a6a5a"
+outline = "#8aaa9a"
+glyph   = "Te"
+
+[buildings.tunnel_exit]
+fill    = "#5a6a4a"
+outline = "#9aaa8a"
+glyph   = "Tx"
+
 # -----------------------------------------------------------------------------
 # Stations
 #