"Firing once launches a large projectile; firing again causes it to detonate."
The Nova is the second weapon found in the game. On the first button press, it fires a single projectile that, on a second button press, explodes and launches six more projectiles. If the firing button is not pressed a second time, the projectile will behave normally, travelling until it's reached it's distance limit, damaging an enemy, or disappearing upon hitting a wall.
The Nova is found in the upper-right section of Eribu. The player must find it in order to progress through a security laser.