multiple bubbles, one above the other. Such stacks are read from the top down. Lettering Traditionally, a cartoonist or occupational letterer would draw in all the individual letters in the balloons and sound effects by hand. A modern alternative, used by most comics presently and universal in English-translated manga, is to letter with computer programs. The fonts used usually emulate the style of hand-lettering. Traditionally, most mainstream comic books are lettered entirely in upper-case, with a few exceptions: Name particles such as de and von, and the "c" in a surname of Scottish or Irish origin starting with Mc. To indicate a frightened or quiet manner of speech. An interjection such as "er", "um", etc. When hand-lettering, upper-case lettering saves time and effort because it requires drawing only three guidelines, while mixed-case lettering requires five. For a few comics, uppercase and lowercase are used as in ordinary writing. Since the mid-1980s, mixed case lettering has gradually become more widely used in mainstream comic books. Some comics, such as Pearls Before Swine, also use lowercase speech to mark a distinctive accent (in this case, the male crocodiles’ accented speech, opposed to all other characters who use standard uppercase speech). From 2002 to 2004, Marvel Comics experimented with mixed-case lettering for all its comic books. Most mainstream titles have since returned to traditional all upper-case lettering. For many comics, although the lettering is entirely in capital letters, serif versions of "I" are used exclusively where a capital I would appear in normal print text, and a sans-serif (i.e., a simple vertical line) is used in all other places. This reduces confusion with the number one, and also serves to indicate when the personal pronoun "I" is meant. This lettering convention can be seen in computer fonts designed for comic book lettering, which use OpenType contextual alternates to replace the single-stroke “I” with a serifed one in appropriate contexts. Substance of balloons In several occasions, comics artists have used balloons (or similar narrative devices) as if they have true substance, usually for humorous meta-like purposes. In Peanuts, for example, the notes played by Schroeder occasionally take substance and are used in various ways, including Christmas decorations or perches for birds. Sometimes balloons can be influenced by the strip's environment: in the Italian strip Sturmtruppen they freeze and crack when the temperature is very low, or an Archie comic strip where two men from