-Based on a freecodecamp tutorial for making tic tac toe in react.js. -Built using create-react-app for ease initially.

// start by creating a 3x3 board, as with tictactoe, then alter it to make a 9x9 board. // Meaning, draw the squares, set the squares up with an onClick input detector and // error-checking. // still run arrays for each 3x3, etc? //need an algorithm for generating all numbers...

//to generate starter numbers, generate "random" solvable puzzle (all numbers), then remove //some numbers to leave a solvable puzzle. //render this solvable puzzle (not all numbers). //retain all numbers in arrays, for error-checking? or just simple checking?

//further functionality: //generate random starter numbers, and determine how many for easy or hard settings. // minimum starter numbers should be 17 - to ensure only one possible solution. //handle game over and allow restart.

//User Function: // each click selecting a square must allow input of only numbers 1-9. // each 3x3 square must have handling to recognise error when same number entered twice. // each row and column of 9x9 must have error handling so no number entered twice.

// // board array layout (pipes for visual clarity): // a0,a1,a2 | b0,b1,b2 | c0,c1,c2 0 1 2 | 3 4 5 | 6 7 8
// a3,a4,a5 | b3,b4,b5 | c3,c4,c5 9 10 11 | 12 13 14 | 15 16 17 A | B | C // a6,a7,a8 | b6,b7,b8 | c6,c7,c8 18 19 20 | 21 22 23 | 24 25 26 // // d0,d1,d2 | e0,e1,e2 | f0,f1,f2 27 28 29 | 30 31 32 | 33 34 35 // d3,d4,d5 | e3,e4,e5 | f3,f4,f5 36 37 38 | 39 40 41 | 42 43 44 D | E | F // d6,d7,d8 | e6,e7,e8 | f6,f7,f8 45 46 47 | 48 49 50 | 51 52 53 // // g0,g1,g2 | h0,h1,h2 | i0,i1,i2 54 55 56 | 57 58 59 | 60 61 62 // g3,g4,g5 | h3,h4,h5 | i3,i4,i5 63 64 65 | 66 67 68 | 69 70 71 G | H | I // g6,g7,g8 | h6,h7,h8 | i6,i7,i8 72 73 74 | 75 76 77 | 78 79 80 // // this will allow checking of each 3x3 AND each row and column.

//error checking: // each 3x3, similar to tic tac toe, if [] contains.... // each row: each 3x3: // a0,a1,a2,b0,b1,b2,c0,c1,c2 0,1,2,3,4,5,6,7,8 0,1,2,9,10,11,18,19,20 // a3,a4,a5,b3,b4,b5,c3,c4,c5 9,10,11,12,13,14,15,16,17 3,4,5,12,13,14,21,22,23 // a6,a7,a8,b6,b7,b8,c6,c7,c8 18,19,20,21,22,24,25,26 6,7,8,15,16,17,24,25,26 // d0,d1,d2,e0,e1,e2,f0,f1,f2 27,28,29,30,31,32,33,34,35 27,28,29,36,37,38,45,46,47 // d3,d4,d5,e3,e4,e5,f3,f4,f5 36,37,38,39,40,41,42,43,44 30,31,32,39,40,41,48,49,50 // d6,d7,d8,e6,e7,e8,f6,f7,f8 45,46,47,48,49,50,51,52,53 33,34,35,42,43,44,51,52,53 // g0,g1,g2,h0,h1,h2,i0,i1,i2 54,55,56,57,58,59,60,61,62 54,55,56,63,64,65,72,73,74 // g3,g4,g5,h3,h4,h5,i3,i4,i5 63,64,65,66,67,68,69,70,71 57,58,59,66,67,68,75,76,77 // g6,g7,g8,h6,h7,h8,i6,i7,i8 72,73,74,75,76,77,78,79,80 60,61,62,69,70,71,78,79,80 //each column: //a0,a3,a6,d0,d3,d6,g0,g3,g6 0,9,18,27,36,45,54,63,72 //a1,a4,a7,d1,d4,d7,g1,g4,g7 1,10,19,28,37,46,55,64,73 //a2,a5,a8,d2,d5,d8,g2,g5,g8 2,11,20,29,38,47,56,65,74 //b0,b3,b6,e0,e3,e6,h0,h3,h6 3,12,21,30,39,48,57,66,75 //b1,b4,b7,e1,e4,e7,h1,h4,h7 4,13,22,31,40,49,58,67,76 //b2,b5,b8,e2,e5,e8,h2,h5,h8 5,14,23,32,41,50,59,68,77 //c0,c3,c6,f0,f3,f6,i0,i3,i6 6,15,24,33,42,51,60,69,78 //c1,c4,c7,f1,f4,f7,i1,i4,i7 7,16,25,34,43,52,61,70,79 //c2,c5,c8,f2,f5,f8,i2,i5,i8 8,17,26,35,44,53,62,71,80

//Long way first - create blank board, create 9 arrays, one for each 3x3 square. create one array, as simpler //to look for error patterns. // To begin with, generate numbers by user input. //Then figure out error-checking. //Then try to add randomising into each array generation, then error-check results to be left with a //solvable puzzle. //Then work out removal of numbers.