Hart hailed City's display as "the right way to play" after goals from Raheem Sterling, Fernandinho and Wilfried Bony gave them the convincing win.
"We set up well, we defended well, and we took our chances well," he said.
"It's pretty simple but sometimes ... we've been a little reckless; I think Vinny's (captain Vincent Kompany) said it a few times - we've been a little bit naive and been caught out."
City still have to travel to Italy to face Juventus before hosting German side Borussia Moenchengladbach at the Etihad Stadium, but Hart said the pressure was off.
"I imagine it will be a lot easier ... It's a different way to look at it this time, we can set up a little bit different and we don't have to be as vulnerable," he added.
Since Arab billionaire Sheikh Mansour bin Zayed Al Nahyan bought the club in 2008, City have qualified for the Champions League five times but have never topped their group.
They have failed to reach the knockout stages twice and were dumped out in the round of 16 by Barcelona on two other occasions.
While topping Group D could help them avoid clashing with another European heavyweight in the next round, Hart is not too concerned about who they will face.
"We're in the competition to win it so at some point we're going to have to play one of those strong teams," he said.
City now have to turn their attention to the Premier League and Saturday's game against Aston Villa. They top the table only on goal difference ahead of Arsenal and Hart said there was no margin for error.
"We're in Champions League mode but we go to Aston Villa with Arsenal playing well .... We need a result now at Villa," he said.
(Reporting by Simon Jennings in Bengaluru; Editing by Peter Rutherford)
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