Inset the core so its gap to the first ring matches the tile gaps

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

scripts/core.gd

@@ -24,4 +24,5 @@ func explode() -> void:
 
 
 func _draw() -> void:
-	draw_circle(Vector2.ZERO, radius, Params.COLOR_RED, true, -1.0, true)
+	# Inset like the blocks, so the gap to the first ring matches the gap between tiles.
+	draw_circle(Vector2.ZERO, radius - Block.GAP / 2.0, Params.COLOR_RED, true, -1.0, true)