From the title screen reach the first boss without taking damage.
Defeat the Giant Brain without taking damage.
Obtain the Hyper.
Beat the game without losing a life.
Defeat Crabullus without taking damage or damaging it while paused.
Obtain the Crusher.
Go through Area 2's interior to the boss room without taking damage.
Go from Area 2 to the end of Area 3 without taking damage. (And without wall upgrades.)
Defeat Photophage (Area 3 boss) without taking damage.
Obtain the Hover upgrade.
Power up your gun to the highest level.
Defeat Fred without taking damage or dealing damage while the game is paused. Ribbit.
Obtain the Key
Defeat Hard Shell without taking damage or having the strongest gun.
Obtain the Dive upgrade.
Obtain the Turbo Speed upgrade.
Go through Area 6's interior to the boss room without taking damage.
Defeat Frozen Crabullus without taking damage or damaging the boss while paused.
Obtain the Wall 1 upgrade.
Defeat Enhanced Fred without taking damage or damaging him while paused. Ribbit.
Obtain the Wall 2 upgrade.
Obtain the upgrade that lets the tank shoot through walls.
Obtain the Infinite Hover upgrade.
Obtain the Prism Shield upgrade.
Obtain the Barricade Blaster.
Obtain the Plasma Cannon upgrade.
Obtain the Spike Guard upgrade.
Obtain the Hover Boots.
Defeat the Underworld Lord.
Have 10 Lightning Bolts in inventory.
Have 10 Triple Warheads in inventory.
Have 10 Homing Missiles in inventory