Drupal is meant to be a dynamic website platform (that runs quite well out of the box) yet customizable.
Despite the good advice to create a "sub theme" by copying and pasting the current files into a new folder i went ahead and hacked at the core php and css...
While Garland itself (I'm using the "configurable sub theme Minelli" which must be modified through Garland) is very hard to work with (I will probably end up using Zen to get my final customized effect)...
FTP into your website hosting and ... /drupal-root/themes/garland
Modifying page.tpl.php with my trusty notepad2...
HTML forms are quick way to get user data but PHP requires a PHP server. Luckily I have one and together it's quite easy to create a page that gets some info from a user and then does some calculations (in this case nothing fancy).
I've done a little more User Input Sanitization than usual - basically the rule is: "If you'll display it, clean up the HTML output, if you'll send it to a linux script, strip the slashes, and if you send it to a database, clean up any MySQL stuff"...
I'm a little sick so this one took longer than it should have. Futher exploration of the theme of PHP + CSS + HTML as a very simple way to get user input and then do something fun with it.
The beginnings of trying to "modularize" code into functions earlier in the process (in later, more complex programs it is a necessity).
You may be asking, "How is this useful?" but I think it's a popular misconception that Programs should be useful...
PHP is similar to C which makes it easy for me to do interesting things. The php manual webpage is brilliant! Don't you wish everybody had a full public API, easy menus, working examples, searchable and with the best user comments that really flesh out the bugs?
CSS is so much better than HTML tables - it really revolutionizes the simplicity, maintainability, and power of displaying things on the web.
Put them together and you have miracles like Drupal.
The following project took a little more time than usual and it might even be useful one day, but I what I really like about it is that it's FUN...