WASHINGTON » President Barack Obama reached out to an online audience Thursday, taking questions on serious subjects like drones and gun violence while also musing about the anachronism of pennies and the "chill" factor in Hawaii.

Participating in a Google+ Hangout chat, Obama offered assurances that drones, the unmanned aircraft used to hunt down terrorists, have never been used against a U.S. citizen on U.S. soil.

"The rules outside of the United States are going to be different than the rules inside the United States, in part because our capacity, for example, to capture terrorists in the United States are very different than in the foothills or mountains of Af­ghani­stan or Paki­stan," Obama said in some of his most expansive comments on the subject.

In 2011, drone strikes in Yemen killed three Americans: U.S.-born cleric Anwar al-Awlaki, his 16-year-old-son and al-Qaida propagandist Samir Khan.

Obama said Congress provides oversight on counterterrorism programs but said he and Congress need to find a mechanism "to also make sure that the public understands what’s going on, what the constraints are, what the legal parameters are."

Asked why the government hasn’t done away with the penny, Obama said he didn’t know, but suspected there was an emotional attachment to the coin.

"We remember our piggy banks and counting up all our pennies and then taking them in and getting a dollar bill or a couple of dollars," he said. "One of the things you see chronically in government is it’s very hard to get rid of things that don’t work so you can then invest on the things that do. The penny ends up being sort of a metaphor for the larger problems that we’ve got."

Asked to reflect about how being raised in Hawaii influenced him, Obama said the islands are a melting pot that exposed him to different cultures and that its climate is conducive to good health.

"The weather is nice all the time," he said. "That kind of chills you out."