Some protection against writing characters we don't have

src/graphics/sprite.rs

@@ -100,6 +100,11 @@ impl SpriteAtlas {
         let mut x = x;
 
         for c in string.chars() {
+            if (c as u8) < 32 {
+                // don't support any ascii below ' ' (space)
+                continue;
+            }
+
             if c == ' ' {
                 x += 4;
                 continue;