Symbolic Sudoku Trivia Quiz

My process for solving a sudoku starts by investigating the symbols (or, more usually, numbers) to see if any of them have enough entries so that the location of any more values can be entered immediately. In this case, there are four such symbols, so any of these first four might be the ones identified at the start.

Looking at the box numbered 1, and knowing that this is supposed to be a straightforward start, I see that this row of the left box must include a !, since each of the two lower rows has one. Looking at the columns which have these two blanks, the right one has a ! above it, so square 1 must be a !.
No further ! entries are immediately obvious.

Square 2 is in a block of nine boxes that has @ elsewhere along the top and bottom rows and in the middle and right columns. This means the middle box on the left must contain a @. No further @ entries are immediately obvious.

The box in the top right corner is in a block of nine that has # in the bottom two rows and the two left columns, leaving this as the only spot for its #. No further # entries are immediately obvious.

Looking at the middle row of blocks, there are $ symbols in the top and bottom rows. Looking at the right column of blocks, there is a $ in the right column. The box numbered 4 is the only space left for the $ in this block of nine.

Looking at Row 7 (which starts with a %), the symbols % and = cannot go on that row in the right-hand block of nine boxes, so they must go in the spots numbered 5 and 6. Since the box numbered 5 already has an = above it, that is where the % has to go.

Now we are starting to get enough information to fill in some more empty squares. A % goes into the bottom right box in the middle column, and another next to the # in the top left block, then the empty spot in the top row of the top right block and the box under the number 8. the last one goes in the right end box of the middle row. That's all of them.

Looking back at the block where the % was entered for number 5, the only place for the = is box number 6.

The righthand block of the middle row is missing its =, which cannot go in the box numbered 7 (which is directly above the one we just entered), so must fit into the blank spot.

Box 7 is the only one in its block for which the symbol has not been determined, so it must be the ?. The left block in the middle row can have a ? placed to the left of Box 8. The only blank spot left in the bottom row of the middle block also gets a ? placed between the @ and the &. In the top row of blocks, the middle one gets a ? in its top right corner.

Box 8 has to be one of =, & or #, the three symbols missing from that block. It cannot be # , which is entered above it in the same column. Neither can it be the =, which must go in the top left box of this block in order for its row to have an =.

That row has # as its missing symbol. The = signs in the left column of blocks go in the middle right box of the top block and the central box of the bottom block.

The only empty spot in the very top row must be +. The only empty spot in the block that had the number 8 is now seen to be a #. The rest of the #s can be placed in the only possible spots for them.

The column that contains Box 9 is missing &, + and $. The bottom box must be $, since the top block already has a $. One of the two spots in the top block must be the +, the other the &. You can work out what goes into a number of the boxes that are still empty, and determine that it must be the +. Or, since you know that there are only nine symbols, and you have placed eight of them, the remaining one must go here.

Finishing the complete solution is now fairly straightforward, and can be worked out in a number of ways, so I won't confuse you by trying to describe how I worked my way through it. The process is basically looking at a row, column or box that only has one or two missing elements, and determining which one has to go where. The more you fill in, the faster this goes!