Here is the full list of all 36 Procyon achievements.
Complete Stage 4 without shield-blocking or being hit by any purple homing bullets on Normal difficulty or higher.
Complete Survival mode on Easy difficulty (or higher)
Complete Stage 3 in Survival mode
Lose a life to the first enemy of the first stage
Complete Attrition mode on Easy difficulty (or higher)
Complete Attrition mode on Normal difficulty (or higher)
Destroy all of the large armada ships in Stage 3 on Normal difficulty or higher
Complete all stages on Normal difficulty (or higher)
Reach the boss of a stage without firing any weapons, using any shields, or dying on Normal difficulty or higher
Sustain a multiplier of 500x for 30 seconds
Kill 20,000 enemies
Block 50 bullets with a single use of the shield
Complete Stage 3 in Attrition mode
Block 500 bullets with the shield
Reach the boss of a stage without firing any weapons
Complete Stage 5
Complete all stages on Easy difficulty (or higher)
Complete any stage without using bullets
Lose your last life during the final boss battle
Destroy 1000 enemies using the beam
Complete Stage 4
Keep the beam locked continuously on a single enemy for 30 seconds
Complete Stage 3
Destroy 50 enemies with one lightning charge
Kill 3000 enemies
Complete Stage 2
Complete any stage without using the beam
Complete Stage 1
Complete any stage without using the shield
Achieve a multiplier of 500x
Destroy 1000 enemies using the bullets
Retry from the Game Over screen
Complete all stages on Hard difficulty
Complete Attrition mode on Hard difficulty
Complete Survival mode on Normal difficulty (or higher)
Complete Survival mode on Hard difficulty