The Voltorb Flip game in HeartGold/SoulSilver replaces the Slots and Roulette in earlier Pokemon games. There is no way to buy Coins in HeartGold/SoulSilver; they have to be earned by playing Voltorb Flip, which does not cost any Coins to play. Voltorb Flip can be quite a challenge, so here are a few tips.
THE BASICS: Voltorb Flip is a logic game, involving a large slice of guesswork and luck. The game board is comprised of a 5x5 grid of cards - the cards are 1, 2, 3 and Voltorb. You start each level with all the cards face-down. At the end of each row and column are two clue numbers, one telling you the sum of all the number cards in that line (the number total), and the other telling you how many Voltorb cards are in that line.
In essence, your task is to use the clues to guess, or deduce, where the 2 and 3 cards are. You must flip over all the 2s and 3s to pass the level and win some Coins. Flip over a Voltorb and, given their tendency to explode when disturbed, it's game over. If you uncover all the 2s and 3s without flipping over a Voltorb, you will receive a number of coins equal to all the 2s and 3s you found multiplied together. (On later levels, that can be hundreds of Coins!)
You must also remember that your Coin Case will only hold 50,000 Coins - if it is full, you will not be able to play Voltorb Flip again until you spend some of your Coins.
HOW TO PLAY: There are two ways to flip over cards: one is by using the touch screen and tapping the cards with the stylus, and the other is by using the arrow keypad and the A button to select cards. Press X to open the Memo and place "marks" on cards you have not yet turned over. When you have found all the 2 and 3 cards on the board, the Coins you have accrued will be added to your Coin Case and you will advance to the next level.
The most important thing you must bear in mind is that a row or column will only contain a 2 or 3 card if the sum of the two clue numbers is greater than 5. For example, if you start the game with the top row containing a number total of 4, and 1 Voltorb, you have no need to flip over any cards in that row. They will either be 1 cards or Voltorb cards.
However, if the sum of the two clue numbers is 6 or more, there must logically be one or more 2 or 3 cards present in that line. These are the lines you have to search in order to pass the level and win the Coins: for instance, if the left-most column contains a number total of 6 and 2 Voltorb, you have to find the 2 or 3 number cards that raise the clue sum higher than 5.
At any point during play, you can choose to quit the level by pressing the B button. Ending a level early will allow you to keep the Coins you have found so far. Quitting a level will not end the game; you will simply restart the level, or you may be downgraded to an earlier level (see Game Levels below for an explanation). To quit the game entirely, you must select to quit before starting a level.
USING LOGIC: To work out when you've cleared a line, remember that the clue sum (i.e. number total plus Voltorb) will always be 5 if there are no number cards other than 1s. If one of the number cards in the line is a 2, and the rest are 1s, the clue sum will be 6. If two number cards are 2s, the total will be 7 - as will be the case if the line contains a 3. And so on. This is true regardless of how many Voltorb are in the line - since they contribute the same amount to the clue sum as a 1 card does. Simply by adding and subtracting, you can work out how many 2s and 3s you have left to find, and deduce where you still need to search, until you finally clear the level (or hit a Voltorb and lose).
As you play, you can use the Memo to mark all the cards in rows or columns that are already "finished", i.e. have no more 2s or 3s to find. (I always start play by marking the rows and columns with a clue sum of 5. I use Voltorb marks for this, since they're least confusing for the purpose.) This is essential as you uncover more number cards - as you find 2s and 3s, you can mark more lines if you've found enough to justify the clue sum of that line. In the example given above - a number total of 6, and 2 Voltorb - the clue sum (8) would be justified by finding a 2 and a 3, or three 2s, in that column. This means that all the remaining cards will only be 1s or Voltorb cards, and the total for that column will match the clues. When you find all the 2 and 3 cards, the column has been cleared, and you can mark the rest of the column because there is no need to search it further. Avoid searching anywhere you don't have to, because that runs the risk of finding a Voltorb, without the possibility of finding more Coins.
As you progress through the game, the higher number totals and more numerous Voltorb make the hidden 3 cards essential clues. On later levels, there may be lines comprised only of 3s and Voltorb (such as a number total of 3 with 4 Voltorb, or a number total of 9 with 2 Voltorb). This rules out the presence of a 2 card, which can be an important piece of information in telling you the right place to search. (You will want to mark the squares in intersecting lines that cannot contain a 3, since those squares can only be Voltorb.) This is also true if a line is partially cleared; you need to pay careful attention to any information provided by the clues that has not yet been accounted for. (For example, if you have a row with a number total of 4 and 3 Voltorb, and you find a 1 in that row, the other number card can only be a 3.) Of course, there will always be an element of guesswork, but the clues can sometimes provide logical certainty. A line of 5 Voltorb, for instance, is a stroke of good fortune - especially if it crosses a line with only one Voltorb, because you know exactly where the Voltorb is.
GAME LEVELS: The game starts at level 1, giving you only a few 2 and 3 cards to find, and not many Voltorb. As you pass levels, there will be more number cards to find and more Voltorb to avoid, making the game more challenging as you progress, but offering an exponentially greater reward. If you uncover a Voltorb and lose the game, or if you choose to quit the level before finishing, you may lose some of your progress: your game level will be set to the number of cards you flipped over before the game ended. If you flipped more cards than your current level, you won't lose any progress. (This is why I recommend flipping over all the cards in any line that contains no Voltorb, even if all those cards are 1s.) If Voltorb was the very first card you flipped over (ouch!), your game level will be reset to 1 and you'll start from the beginning again.
If your luck and logic are good enough, you will eventually reach level 7, the maximum standard level in the game. A specific set of requirements must be met in order to advance to the bonus level: level 8, which is a brain-bending challenge but offers an incredible reward if you can beat it. Level 8 can be reached if you clear more than eight cards when you clear level 7 - but the level advance is random. You may also jump to level 8 if you win five games in a row, but this too is random, and winning five games in a row is rare. You have to be very skilled and very lucky to reach level 8, and even more so to win.
THE REWARD: Scoring, of course, depends on the number of 2s and 3s present on the board, but the reward increases as the game level rises.
Level 1 offers 20-50 Coins;
Level 2 offers 50-100 Coins;
Level 3 offers 100-200 Coins;
Level 4 offers 200-350 Coins;
Level 5 offers 350-600 Coins;
Level 6 offers 600-1000 Coins;
Level 7 offers 1000-2000 Coins.
If you reach level 8, it offers 2000-3500 Coins!
THE PRIZES: The two Game Corners offer different prizes in their Prize Shops. The prize Pokemon also differ slightly, depending on which version you are playing.
The following prizes are available in the Goldenrod Prize Shop.
The man on the left offers prize Pokemon:
Abra (200 Coins)
Ekans (700 Coins, in HeartGold) or Sandshrew (700 Coins, in SoulSilver)
Dratini (2100 Coins)
The man on the right offers hold items and TMs:
Metronome, Silk Scarf, Wide Lens and Zoom Lens (1000 Coins each)
TM90 Substitute (2000 Coins)
TM75 Swords Dance (4000 Coins)
TM44 Rest (6000 Coins)
TM13 Ice Beam (10000 Coins)
TM24 Thunderbolt (10000 Coins)
TM35 Flamethrower (10000 Coins).
The following prizes are available in the Celadon Prize Shop.
The man on the left offers hold items and TMs:
Metronome, Silk Scarf, Wide Lens and Zoom Lens (1000 Coins each)
TM58 Endure (2000 Coins)
TM32 Double Team (4000 Coins)
TM10 Hidden Power (6000 Coins)
TM29 Psychic (10000 Coins)
TM74 Gyro Ball (10000 Coins)
TM68 Giga Impact (15000 Coins)
The man on the right offers prize Pokemon:
Mr. Mime (3333 Coins)
Eevee (6666 Coins)
Porygon (9999 Coins).
That's basically all there is to it. Best of luck playing - may your luck, and your rewards, be great!
I'm glad my guide is helpful.