3. When you have a heap of sand high enough to suit your inner Frank Lloyd Wright, start carving. "Carving tools don't have to be fancy expensive things. Bring old kitchen knives, putty knives, trowels. Then you will want a scooping tool -- a spoon, a melon baller, something that has the round curve to it. Also, something you could cut a groove with, like a fork with just one tine, for drawing surface details."

4. "To build the kind of castle that people will stop and notice, plan to spend two to three hours. And don't forget the sunscreen."

Lucinda Wierenga's Web site ishttp://www.sandyfeet.com. "Sandcastles Made Simple" as well as professional carving tools are available online at the Sons of the Beach athttp://www.sobshop.com.

ROAST A MARSHMALLOW

Let's get this straight right off the bat -- that whole stick-and-fire routine is so, like, over.

That's what your mother did at camp in the Eisenhower era. This is the 21st century, baby. We're talking environmental enlightenment. We're talking zero-emission, reduce, reuse, recycle. We're talking -- you guessed it -- solar-powered marshmallow roaster.

The roaster, promises Simon Quellen Field on his Web site Scitoys.com, "is not just a fun toy, but a toy that teaches important scientific principles." And it will torch a marshmallow faster than you can say "S'mores."

Field is a senior software engineer for Google, and he's the author of "Gonzo Gizmos: Projects & Devices to Channel Your Inner Geek," and president and chief executive of his own company, Kinetic MicroScience, a science toys business. An inventor since childhood ("some of the fires and explosions are undoubtedly repressed memories"), Field offers projects on his Web site from "fun with high voltage" to "a film can cannon." And then there's the marshmallow roaster.

It's constructed from a cardboard box lined with aluminum foil, a flat plastic page magnifier, glue, tape and a skewer to hold the marshmallow (illustrated instructions are online at http://www.scitoys.com/scitoys/scitoys/light/marshmallows/solar_roaster.html ). You could whip a roaster together in 15 minutes, easy. It is likely that interest in eating the marshmallows will take a distant second to interest in seeing how quickly they can be carbonized.

"Most marshmallow toasters are borderline pyromaniacs," agrees Field happily. "But once surrounded by chocolate and graham crackers, the taste of charcoal is barely discernable."