# Slides

Each slide is produced by a slide environment. This environment has a single argument, which is a list of all the colors contained on the slide. For example, a slide that has the colors red and blue is created by an environment

        \begin{slide}{red,blue}
...
\end{slide}


The colors in the argument must have been declared by a \colors command in the root file. They tell SliTeX which color layers to produce for this particular slide. If there is green text in the slide, that text will appear in the black-and-white version, but no green color layer will be generated unless green is included in the slide environment's argument. If you want only black-and-white slides, then you can use a null argument:

        \begin{slide}{}
...
\end{slide}


The text that appears on a slide is produced using ordinary LaTeX commands. You can use any commands that make sense for slides. Commands that don't make sense include sectioning commands, figure and table environments, indexing commands, commands for generating a bibliography, and page-breaking commands. The latter make no sense in a slide because each slide must fit on a single page. You can use an \input command, but not an \include command. Commands for producing only some of the slides in your slide file are described in Making_Some_Slides within this topic.

There are two major differences between the text generated by SliTeX and that generated by LaTeX. First of all, text is automatically centered vertically on the slide. Secondly, and most noticeable, SliTeX uses a set of type faces especially chosen for slides. The characters in these type faces are much larger than the ones in the corresponding LaTeX type faces. SliTeX's \normalsize produces roughly the same size characters as LaTeX's \LARGE. Also, SliTeX's ordinary Roman type style is similar to LaTeX's sans serif style. Besides Roman, the only other type styles generally available are italic (\it), bold (\bf), and typewriter (\tt).

The only commands you need inside a slide that aren't present in ordinary LaTeX input are ones to tell SliTeX what color the text is. The \colors command in your root file defines the declarations for doing this. For example, if the root file contains the command \colors{red,black,blue}, then \red, \black, and \blue are declarations that specify the color. They work just like any other declaration, such as \bf, having the same scoping rules.

A color declaration does not affect the type style.

Text in which there is no color declaration in effect appears on all color layers. For example, if you make no color declarations anywhere in your slide file, then all color layers will be identical to the black and white versions. Note that color declarations are undefined in the root file.

The command \invisible is a special color declaration for invisible text. Invisible text is not only colorless, appearing in no color layer, but does not appear in the black-and-white version either. The use of invisible text is explained below.

WARNING: Don't use a color declaration or an invisible command in math mode.