Fake fireworks
This isn't the right season for fireworks in Norway since it never gets dark enough to see them properly but I do like a good firework display so clicked on a link to this fantastic firework display on Facebook. I've never seen non circular star bursts like this so was intrigued as to how it was achieved. After exploding all parts of the rocket normally travel at the same velocity so would spread out in a spherical pattern, however they are also affected by gravity so the parts travelling down would travel faster that the ones travelling up. A perfectly circular vertical circle would be hard to achieve and a heart shape impossible without the parts having some sort of propellant. The flat heart is the real clincher though, as the parts spread out they should be falling. It's fake.