Draft:Shiren 5 2020:Explosion Rocks

Explosion Rocks (Japanese: ???) is a minigame in Shiren 5. It is a Shiren take on the classic logic game of Minesweeper. You cannot take items into this minigame, so you must store your items at Hotel Nekomaneki or you will lose them. You keep all items you find inside Explosion Rocks upon victory, or if you choose to leave the minigame after beating a floor.

Gaining Access

You can launch Explosion Rocks from the Dungeon Center in Nekomaneki Village. Access is not restricted; you can play as soon as you can reach the Dungeon Center.

Unique Features

Explosion Rocks is basically a Shiren take on Minesweeper. If you're good at Minesweeper, you can probably beat all difficulty levels of Explosion Rocks without knowing much about Shiren at all. If you're not good at Minesweeper, you'll need to learn how to play and master Minesweeper, and you might be able to learn and practice faster with other implementations of Minesweeper elsewhere on other platforms or online. (E.g. the Windows and online versions of Minesweeper let you play much faster than the Shiren version, and thus gain experience and learn how to master it faster.)

Explosion Rocks floors are usually much smaller than bonus dungeon floors. Each floor is rectangular, surrounded by a 1-square-wide water moat border, and what appears to be the usual 1-square-wide unbreakable wall border outside of the water moat. (There is no way to cross the water to try testing the exterior boundary wall.) As in Minesweeper, the higher the difficulty, the larger the floor and also the higher the density of landmine traps. Floors are randomly generated, with a much higher frequency of landmine traps than in bonus dungeons, no other types of traps, and drawing from a very limited set of items and monsters. For some reason, the Squid Sushi Scroll is very common in Explosion Rocks. In fact, scrolls on floors 1-4 are almost always Squid Suchi Scrolls. You can throw a Squid Sushi Scroll at a Squid family monster to turn it into food (an Onigiri), but Squids don't appear in Explosion Rocks, so the only thing they seem to be good for is just carting them out of the dungeon and selling them or possibly using them in dungeons that let you take items in. Well, if you ever wanted to collect a large number of Squid Sushi Scrolls for whatever reason, Explosion Rocks is the place for you. Floors 1-4 all seem to be generated using the same algorithm, placing exactly 6 items (on Expert mode) randomly about the floor, drawn from a variety of grasses, the Squid Sushi Scroll, some other scrolls (very rarely), and Gitan bags. Floor 5, the final floor, has 15 items (on Expert mode), drawn from a wider set of possible items, and the items tend to be much more valuable as well.

Most squares in the playfield start covered with breakable walls. All empty squares and landmine traps begin covered in breakable walls, and any monsters that exist are also on top of landmine traps and thus also covered by breakable walls. These monsters are unable to move or do anything until you break the walls covering them. (Open question: did they start in a paralyzed state, or is this just the effect of being covered by a breakable wall? It's unclear.) But once a monster is revealed, it moves and attacks as normal after your next turn. The only squares that aren't covered with breakable walls to begin with are Shiren's starting square (one step NE of the SW corner), the exit stairs (one step SW of the NE corner), and the few squares with pre-placed items on them scattered about the playfield. (You can never find items under breakable walls in Explosion Rocks, just empty space, a landmine trap, or a landmine trap with a monster on top.)

As in classic Minesweeper, when you break a wall that has open space underneath, it either shows you a number from 1-7 which is the number of landmine traps around that location, or, it shows blank floor meaning there are 0 landmine traps around that location. If 0, all adjacent breakable walls are also removed as a group, and this is repeated recursively if any new "0" locations are revealed. (In this case, they all disappear as a group all at once.) Why only numbers 1-7 instead of 0-9? In most modern Minesweeper variants, showing the 0s is considered needlessly cluttering, and if you talk to the old lady in the Dungeon Center who runs the Explosion Rocks game she says the maximum value is 7, which presumably means the game does not allow squares with 8 or 9 mines around them to be generated. (Numbers are not shown for squares that have mines on them, so you could never see a 9 even if the game generated a level that way and even if you had a way to safely uncover it. Likewise, if the game did generate a square with 8 mines around it, you could never reach it.) Spaces that contain items and thus start uncovered by breakable walls also show a digit (or no digit for 0), though it can be hard to read until you pick up the item. Shiren always starts on a "0" location, so it is safe to open all the walls immediately around Shiren's starting position. No digit is shown for the stairs location, or perhaps the stairs just fully cover the digit on the floor underneath, but the stairs are not always a "0" location.

(Note that, across Shiren 5, breakable walls are apparently generated in groups. If you hit a breakable wall that is part of a group, the entire group falls all at once. So, in a bonus dungeon, you can reveal an entire hallway this way—but not all connected hallways or all connected rooms that are also covered with breakable walls, as these are apparently different breakable wall groups. In Explosion Rocks, most breakable walls are apparently in groups of just 1 breakable wall, but a set of connected 0-mine locations are in a group together so they all fall together as well.)

If you open a breakable wall with a monster on top, (a) there is a landmine trap there as well but it doesn't go off and (b) the monster is set loose to begin moving after your next turn, so you have one turn to react to the appearance of the monster. If you open a breakable wall with a landmine trap on it and no monster, the landmine trap detonates, bringing you down to just 1 HP or killing you if you were already at 1 HP. A landmine trap detonation does not break any of the adjacent breakable walls, but it does kill any adjacent, revealed monsters.

As in most Minesweeper implementations, you can tag spaces as known landmine traps, in this case by using the cursor joystick to highlight the wall in question and the left shoulder button to toggle it as a known mine. There is no counter of remaining untagged landmine traps however. Most Minesweeper implementations allow you to open locations anywhere on the playfield, but in this one, you usually need to move Shiren horizontally or vertically adjacent to the location you want to open and punch it. Punching diagonally doesn't break the wall, nor can you move diagonally if there is a wall space in either of the other 2 spaces that share the same corner, which makes it slightly more difficult than other Minesweeper games where the player has a presence on the board and where diagonal moves are allowed. (You can move diagonally if the 2 spaces that share the same corner have no wall, even if those spaces have landmines on them.)

You start each game of Explosion Rocks with a small, fixed set of items every time: one Large Onigiri and two 4-2-8 explosive pots. (It's possible the Large Onigiri comes from unlocking something in one of the Starting Villages that gives you a Large Onigiri at the start of every dungeon, rather than being something specific to Explosion Rocks. The two explosive pots on the other hand are definitely unique to Explosion Rocks.) The explosive pots can be thrown at walls from a distance. As usual, you can throw them a maximum of 10 spaces, and they will stop before 10 spaces if the next space is not open. Then the pot explodes, destroying itself + all breakable walls + all items + all monsters in the 3x3 area around where the pot stopped moving. (Open question: can a monster ever survive such an explosion? It seems that all monsters, no matter how strong, always die immediately when next to an explosion. This is definitely true in Explosion Rocks—none of the monsters are particularly strong anyway.) Thus you can use the pots from a distance to open more squares without taking damage from landmine traps, monsters, or the explosive pot itself.

As in a storage location, Shiren doesn't heal by moving or passing turns in Explosion Rocks. Also, Shiren starts with a full belly, but it is possible to die of starvation if you take too many turns playing the minigame.

Final Reward

You do not get a reward item for winning Explosion Rocks, but you do get to keep items and Gitan you have on hand if you win. See Farming Opportunities below for more details. You get a PSVita trophy if you beat all difficulty levels at least once, and the game keeps track of how many times you've won in the Adventure Footprint (combined across all difficulty levels, and not as a percentage of attempts).

Farming Opportunities

Best Bets

If you're good at Minesweeper, this may be the fastest and best way to get a Heal Bracelet, which is one ingredient necessary for one great sword rune. Likewise, it may be one of the fastest ways to get a Growth Bracelet, though this isn't a rune ingredient. You can also farm out other good rune materials and other helpful common grasses here, perhaps more quickly than you could farm them from other locations. (A good alternative for equipment is Merchant's Hideout, and a good alternative for common, helpful grasses is just the Tower of Fortune itself, possibly escaping out as soon as you've found the item(s) you're looking for.)

Depending on what you're trying to farm, you may be able to find it quickly and exit before reaching 5F, or you may need to beat the entire minigame. See below for more info.

Statistical Analysis

The initial author of this webpage ran an experiment where he tracked every item he found across 5 complete and successful runs of Explosion Rocks on Expert difficulty then tallied them up. (Caveat: across these 5 runs, he missed exactly 2 Gitan bags and no other items. Given every other Gitan bag has always been exactly 150 Gitan, he assumed these 2 missed bags were also 150 Gitan each.) This probably isn't enough runs to have strong statistical significance, but still, it can help you see what kinds of items you might expect to find at different depths of Explosion Rocks. The results are in the chart to the right, and the source Excel spreadsheet is here: https://1drv.ms/x/s!ApAatWNAqJ5viOZZNhfrS-uHBFrPrg.

Note that on floor 1-4F, aside from Squid Sushi Scrolls, you tend to find common/cheap grasses. Some of these are rune ingredients, but not rare ones, and they may be more useful just to help you survive and win your game of Explosion Rocks. But on 5F, you get substantially more valuable items, many of which are helpful as rune ingredients or with crafting in general.

Strategies

Most players should have no trouble beating Novice and Veteran difficulties, so these tips are written for Expert difficulty. Even Expert won't be much of a challenge for players who are already strong at Minesweeper logic puzzles. If you're not good at Minesweeper yet, you can find tips and faster practice games elsewhere on the web. You don't need to know any special Shiren knowledge to win even at the Expert level, but it can give you an advantage.

The single Large Onigiri you start with is plenty to make it all the way through all 5 floors without starving, provided you don't waste it by eating it too early or wandering around on the floor aimlessly trying to figure out your next move. Note that if you're holding any type of Onigiri when you detonate a landmine trap, it becomes a Grilled Onigiri. It's unclear which one is better. The Large Onigiri refills your entire stomach, giving you more than enough time (turns) to make it through all 5 floors with plenty to spare, but the Grilled Onigiri gives half as much food value but also heals you, which can help you survive another mistakenly revealed landmine trap. You could place the Large Onigiri on the ground far away before you take a risk opening up a wall that you're not sure of, to keep it un-grilled, but it's probably slightly better to keep it with you and let it become a Grilled Onigiri to give an extra healing opportunity. Food starts getting a little tight towards the end, but you usually also find plenty of grasses to supplement your diet and make it through to the end without starving. If you do put the Large Onigiri down to avoid grilling it, don't forget to pick it up again! It can be hard to see items on the ground with all the digits and marked bombs on the map.

Try to avoid using your explosive pots on early floors, especially floor 1. If you have to use them so early, odds are lower that you'll be able to make it through all 5 floors safely. Since you haven't really accumulated anything of value, or spent a lot of time on the attempt so far, just go ahead and take risks earlier on if you need to, to save your explosion pots for floors 3 and 4. If the risks turn out badly, you can just restart without losing much progress. 5F (the last floor) is actually much easier than other floors, as there are 15 squares with items rather than just 6 (on Expert difficulty). So, if you make it to floor 4 and are thinking about taking a risk or using an explosion pot to lower the risk, that's a great time to use the pot to lower the risk. (OTOH, you do keep all your equipment when you leave, so if you really want a 4-2-8 explosion pot elsewhere, you could take the risk and hope to keep the pot to take out of the minigame.)

Of course, when you need to take a risk, it's good to take the most useful risk and/or the risk with the best odds. E.g. you'll sometimes be in a situation where you are forced to take a risk somewhere, but some walls have a 2/3 chance of having landmine traps, while others have 1/2 chance, and still others have 1/3 chance. All else being equal, take the 1/3 chance. But all else is not always equal. Sometimes it would really help to prove out a lot of things if you just knew which out of a pair of squares had a landmine trap, and in that case, maybe it's best to just take the higher risk. You can survive multiple landmine traps and/or monsters if you manage the items you pick up along the way wisely.

Most of the items you can find on floors 1-4 can help you survive in various ways:

• Use Invincible Grass immediately before you need to take a risk. If a monster is revealed, you can kill it safely, and if a landmine trap goes off, you'll take no damage. Then keep opening up more risky squares while the invincibility lasts. Just beware of revealing a monster right as your invincibility ends. It lasts maybe 20(?) turns (confirm this!), so stop going crazy a few turns before it would run out.
• Though rare, you can sometimes find a Navigation Scroll on floors 1-4. You can read it and display the map at largest size to see where all the monsters are underneath walls, and tag these locations as known landmine traps. This can greatly reduce the risks of that floor.
• If you reveal a monster, eating a Swift Grass is 100% safe, because the monster won't act until after your next action. If you have a long retreat path, you can back up, hit the monster, back up, hit the monster, repeat as necessary, and kill the monster before the Swift Grass runs out. Do this a few times and you'll level up and get more HP.
• Dragon Grass will of course kill a monster you're facing in one shot.
• Cheery Grass will level you up and give you more HP. If you wait to use this until after you set off a landmine trap, you'll level up and get ~4 HP back, which means you can survive another landmine trap.
• Likewise, it's probably best to wait to eat Heal Grass until after a landmine trap, so you can survive another landmine trap.
• All the negative grasses can be thrown at monsters to help beat them, but of course you might miss.
• All the positive grasses can be eaten when you're not already full to give you more food value / let you survive longer.

If you reveal a monster, running away doesn't heal you. You can try to fight it hand-to-hand, and/or use items. It would be a shame to waste an explosive pot, but so long as you have more than 1 HP, using the explosive pot will kill the monster and you will survive.

There are several ways to heal yourself, which lets you survive more mistakes and more risks that turned out poorly. You can find Heal Grass on floors 1-4. The Grilled Onigiri will heal your hit points too. And you can find a Growth Bracelet on 5F which levels you up and gives you more hit points that way. But the passage of time doesn't heal you, nor does a Heal Bracelet which can also be found on 5F. Don't make the mistake of putting on the Heal Bracelet, because not only does it not heal you, but it makes you digest food faster.

Items cannot be found underneath breakable walls, so if you've picked up every visible item already, there's no reason to try to clear more area, just proceed as carefully and quickly as you can to the exit, as this will also help you avoid starvation. Alternately, you may find that you can exit safely, but you'd need to take at least 1 more risk in order to get 1+ remaining items, and in that case you'll have to weigh the costs/benefits. Generally speaking, it's vastly better to leave behind any items on floors 1-4 rather than take even a small risk, as there's never anything of great value on these floors. 5F, on the other hand, has much better loot, including some weapons, armor, and bracelets that are either very rare or impossible to find in Tower of Fortune main dungeon (but which can be found in other locations).

If you want to get fancy, you can either leave Gitan bags on the floor or swap them with an item in your inventory to get the Gitan bag into your inventory, to use them as projectiles against monsters. Gitan bags in Explosion Rocks are always exactly 150 Gitan, so should do exactly 15 HP of damage to a monster if you don't miss. But the game isn't that difficult, and if you're a strong Minesweeper player, you likely won't need such optimizations to win.

Theoretically, you could deliberately trigger a landmine trap to destroy any revealed monsters adjacent to the trap. So long as you have more than 1 HP, you will survive the blast yourself. You could do this with revealed landmines or with covered spaces you hope have a landmine and no monster on them. But, even if this works, it will put you at 1 HP, making you vulnerable to subsequent landmines, so it's better to find other ways to deal with any revealed monsters if you can (e.g. with items) and only use this trick as a last resort. (OTOH, if you were planning on using an explosion pot to do the same thing, you might as well use a landmine trap and save the explosion pot so you can throw it at remote walls to safely drop many walls at once.)

Don't forget to use the landmine tagging feature, it helps a lot. Move the cursor joystick over the spot you know is a landmine and press the left shoulder button.

Don't forget to sell or store everything, including Gitan, before you start playing and between runs! Anything in your possession when you start playing will be lost/destroyed.