For three days in February, playwrights, critics, actors, theater lovers and theater professionals thronged the Denver Center Theatre Company complex, watching staged readings, attending performances, listening to panel discussions and holding animated debates of their own over breakfast pastries or lunchtime salads and sandwiches. The Denver Center's New Play Summit, which got its start in 2006, becomes more sophisticated and attracts more national attention every year. Several plays that began their life as readings at past summits have been staged by the company; artistic director Kent Thompson has selected three of this year's plays for his coming season.