Period 6-1[edit]
Compared to the considerably long boards that you were recently subjected to, this stage will be comparatively shorter. While you might be interested in bombing around for items, you may wish to simply plow through the stage. In that case, you can almost make it half way through the entire stage by shooting a Hyper Missile down the bottom or top rows of the stage and chase after it until it hits the wall. To advance beyond the wall, you need to bomb the section four blocks down from the top (1) several times in order to create a gap to pass through.
The end of this stage is far more dangerous with watery corridors to navigate through. Fortunately, you can find a number of Waterproof items in the area before you have to set foot in the water. Use one, in conjunction with a Super Charger to help you move faster through the water and get more use out of the item. As the map indicates, you must bomb all four of the individual blocks along the water a couple of times in order to progress from one corridor to the next, (2) through (5). Additionally, the key isn't hidden beneath any of the regular bombable blocks, but rather one of the wall sections along the bottom of the first water passage.
Pay close attention to the appearance of the water at your feet as you move around. If it starts to blink, it means that your Waterproof item is about to expire, and you should proceed to safety, or activate another one. After you bust through the corridors, if you have enough time left on the use of your Waterproof item dash up to the wall below (6) and bomb it to create an entrance to a treasure room. Provided you don't bomb the third statue from the left, you can find a Flash, a Megaton Bomb, and another Waterproof item. Good thing too because you're going to need to use it when you return to the main stage, in order to safely reach the exit without drowning.
Period 6-2[edit]
This stage is a bit like the ones you've seen that have nothing to bomb for a long time, followed by two full screens of blocks. However, the emptiness is very brief in this stage, lasting only one screen. From then on, it is completely full of blocks. Not only that, but it loops around, so you'll have to be on the lookout for the Chalice. Hyper Missiles will be your best friend in this stage.
In order to find the Chalice, you should look for a suspicious looking block in the middle of certain hallways (1). When you begin to approach it from the left, you will be forced to enter an underground tunnel, which isn't such a bad thing. The tunnels in this period are shorter than usual, so it shouldn't take long to explore, and hopefully you'll pick up some items and points along the way. Once you are back out, continue bombing the blocks until you reach the solitary wall. Bomb it until it disappears, and you'll find the Chalice underneath the block immediately following the wall.
When you finally reach the end of the stage, it is unlikely that you will discover the key without discovering the entrance to the treasure room (2) since the Key is hidden directly below the suspicious looking block in the wall. When you head up, you will find ten statues, six of which contain items. If you know which statues not to bomb, you can collect all six and return to the stage below. When you're ready to exit the stage, bomb either of the separated blocks along the wall, (3) or (4). Pay close attention to their location, because this will help you reach the exit in the next stage.
Period 6-3[edit]
This period can be frustrating, not due to the concentration of blocks (or cones in this case) that you must destroy, but because you are required to discover the correct locations to bomb in order to proceed through the stage. This is a dark stage, which you can easily alleviate with a Lamp, provided you have one. Furthermore, this is a looping stage with a fairly well hidden Chalice. It is important to take your time and discover everything you can about this stage.
Eventually, you will make it to a section of the stage where the blocks distinctly spell out the word "HELP." Indeed, help is what you'll need because you will be forced to find a way to navigate through the letters in order to proceed to the right. The map indicates the correct positions along the "E" (1) and the "L" (2) to bomb several times in order to make a hole that you can pass through. However, when you get on the other side of the word, you can receive help in the form of the pond inside the "P". Bomb the right side of the "P" (3) and step in the water to destroy your enemies and double the count of many pieces of your inventory.
Eventually, as you proceed to the end, you will be forced to pass through a narrow corridor through the center of the stage. Be careful not to travel too far to the right as you exit the corridor and scroll the screen too far. It turns out that the Chalice you are seeking to end the looping is directly below this corridor, back to the left. If you scroll to far, you will scroll it out of sight and be forced to repeat the loop in order to find it again. Just beyond where you collect the Chalice, you will come to another nearly impassable wall. Once again, you must discover the correct location to bomb (4) in order to proceed.
Once you have collected the Chalice and can successfully approach the exit, you will reach another solid wall. The points that you can bomb to pass through to the right side are identical to the points that you could bomb in the previous stage; they just aren't explicitly indicated on the wall. Bomb through either (5) or (6) and clean up the area beyond to find the Key and escape the level. By the way, it is valuable to head into Period 7-1 with as many bombs as possible, so stick around and stock up if you need to.
Boss[edit]
The boss of the Period is known as Aqua Brain, a damaged control computer. It wanders around the room at high speeds, firing bullets out all around itself. When the bullets land, they explode and out come little whale missiles that travel in straight lines along the ground in search of a target to hit.
Despite being damages, the Aqua Brain has considerably good aim. Therefore, trying to take it out slowly with your regular gun isn't a viable option unless you have a large number of Extra energy items that you don't mind wasting. It is better to rely on bombs or Hyper Missiles. 6 direct hits from the missiles will destroy it. Otherwise, just lay bombs close enough to catch it in the blast. Eventually, it will explode, and you will proceed to the next Period.