Please note that you should have already completed third chapter as the area with this achievement contains spoilers about the rest of the game (And if you're curious: Heroic dance is NOT a pc achievement, so you don't have to try unlocking it). You can find entrance to the area under the Chapter 3 start point as seen on the screenshot (small light is Mi inside the tunnel).

When you enter it you should get down to the well looking like this:


Continue going down until you reach an activation light, activating it will send you to an area outside of Chapter 3 underground where you will find an achievement and 2 other secrets.

You will find yourself inside a cave. Fall down the hole until you reach the bottom.


Go to the right till you reach this room:


Notice that you can also control the ball in this area. Use that ability to go up the tunnel. Proceed further till you reach another room with a tunnel up on the ceilling.


To reach it you have to climb a wall to the right, change to the ball form while holding left and up, when you get close to the wall on the left change back to mi so you can climb up the tunnel and go further.
This section will have beat-oriented puzzles:

Listen to the music carefully or count the time between shots of the laser, every time the drone shoots, you have to be behind a cover, otherwise you'll have to begin from the start.
As soon as the laser stops shooting, proceed to the right and change to the ball accelerated with UP button, so that you can reach the hole on the right. Wait until the next laser stops and quickly jump out of the hole, while making the same ball manouver to get to the wall on the left. Climb it and hide behind cover before the laser shoots. Use the ball again to get to the platform above and proceed to the right.


Now this room is a bit tricky. You have to watch out for the laser all the time, as you try to activate the button. Load it up to the max while repeatedly climbing up on it after laser shots, and falling down before it fires again. When it's fully loaded and the laser has finished, you have to quickly rush to the hole in the wall on the right as a ball. When it stops again, you have to climb out of the hole and jump as a ball on the wall above, good ensurance that the laser won't hit you is jumping to the small wall on the left and waiting for the button to deactivate. When the floor is back again, go to the right where the crucial part about unlocking the achievement awaits.


You see the light in the wall? You have to contain your desire for going down and climb inside the small hole in the wall using the ball. There you have to go up through the hidden tunnel and go through some boring and perfectly safe caves. Once you drop down certain hole, you'll se a beat-activated lava floor, like this:


You can see a hole in the ceilling on the left, if you're up for YET ANOTHER DIFFICULT FIGURE CHALLENGE, you can enter it earining absolutely no steam achievements. Otherwise go to the right normally.


In this room you have to stick to the wall on the left when lava is about to activate, climb it normally when it's cold and dry so that you reach the safe right part of the room. Then climb up the tunnel above.


As you can see, this room will be about manouvering accelerated ball, when it's safe- go up the right wall, drop the accelerated ball on fresh deactivated lava and steer it to collect the white pickup after the first bounce, then bounce left and grab the edge before the drone. Climb it fast yet carefully and shoot the drone down. With the clear path go to the left.


The small wall sticking from above in front of you sends you to YES, YET ANOTHER FIGURE CHALLENGE. Unless you want to accomplish it without earning a steam achievement, ignore it.
Pick up the red glowing thing right before the lava deactivates, and rush left to the small tower part of the maze. Release the launching pick up just before the lava activates, so that you'll drop once it already dried up. Then go to the left.


This is the last trial you absolutely have to face. It's not really that hard once you find the safe moment of the rythm. 4 lasers will launch, then the machine will burst white projectiles around the room, and at last the lava floor activates, after all that- there is a short safe period of the cycle during which you'll have to go inside the maze and hide under the rock roof in the middle (above which the bursting drone is hovering). The cycle will run once again, and during another safe period, you need to climb the roof, then hide between the small rock and the den above the bursting drone. Wait till another cycle ends and rush to the T wall on the left and hide below it, before another cycle starts. Then you will be able to safely continue down.

Congratulations, you unlocked PEW!PEW! achievement. If you continue down you will start from the aforementioned crucial point, and face some more beat-oriented challenges in order to discover a conclusion to the plot of this small chapter (if some will insist, I may try to cover that part as well). If you can't be bothered to do it, you can just drop to the main menu by exiting the game to the chapter selection using ESC key.


Thanks and have a nice day. ~ Shuvack