Tegan and Sara make catchy songs about loving not wisely but too well. They’ve defined themselves with sunny, self-loathing power pop, peaking with 2007’s The Con. Here, the girls just wanna have fun: With squawking synths, clipped vocals and head-snapping New Wave drums, their latest is an Eighties dance party. “Alligator” recalls early Madonna, “Red Belt,” Eighties post-punk. The chirpy “Go steady with me!” chorus of “On Directing” makes you wonder what Toni Basil is up to lately. That’s not to say happiness rules. On “Northshore,” they cap a laundry list of “don’ts” with the declaration “My misery’s so addictive!” True, that.