Double click the green flag Use your mouse to avoid the sword. Once you get the boss to low enough health, well, try not to rage ;) Power ups will randomly appear on screen, the blue-ish one gives you a shield and will take one hitpoint before it disappears, another power up looks like a sword, click this one to cause double damage for a short amount of time, lastly, a yellow-ish power up will cause the boss to be stunned/dazed for a short amount of time. This boss-fight is moderately hard since you only have one life to beat it. Given the difficulty, I'll suggest some strategies to make it easier, keep your distance from it and learn it's attacks over time. Take your mouse out of the screen to achieve invulnerability, however, the boss will start regenerating health when your pointer is absent.
This is a three-quel to "Diamond Gear Bossfight" ( https://scratch.mit.edu/projects/500469502/ ) Music: Simple Sight - Piercing Lazer