I think an update broke this. Use WASD to move. Use space to block. Click to shoot. Press C to use a smaller shield that can knock back the boss's projectiles, allowing them to still damage it. Avoid the boss's projectiles and the spikes that come out of it.
@ThePhantomAnimator for player health bar. @anexus for boss health bar. Do not forget to follow! I need your support! Try to No-Hit this.