At the end of a long driveway that winds through sprawling meadows and cornfields, a sculpture of a smiling Humpty Dumpty, perched on a wall, beckons visitors into the front door of the health care technology company Epic Systems Corp. It is the first of many unconventional pieces of art here at Epic's headquarters, where office buildings are designed to mimic Midwestern farms, city subways, tropical forests, and magical castles. Amid these whimsical trappings, in thousands of private offices with doors closed and blinds drawn, youthful programmers in T-shirts and sandals write code for the software that holds medical data for millions of Americans.