solutions now really solvable

script.js

@@ -57,11 +57,18 @@ class Board {
     this.SCREEN_PAD = 20;
 
     // Orb grid
-    this.grid = {};
+    this.grid = [];
-    this.tiles = {};
+    this.tiles = [];
 
-    this.onOrbClick = (index, orb) => {};
+    for(let i=0; i<120;i++) {
-    this.onTileClick = (index) => {};
+      this.grid[i] = null;
+      this.tiles[i] = null;
+    }
+
+    this.onOrbClick = (index, orb) => {
+    };
+    this.onTileClick = (index) => {
+    };
 
     this.initOrb();
     this.initGlyphs();
@@ -163,7 +170,7 @@ class Board {
    * @returns {{x: Number, y: Number}}
    */
   gridIndexToXy(index) {
-    return { x : index % 11, y: Math.floor(index/11) };
+    return {x: index % 11, y: Math.floor(index / 11)};
   }
 
   /**
@@ -199,7 +206,7 @@ class Board {
   removeOrbByIndex(index, errorIfEmpty = false) {
     if (this.grid[index]) {
       this.$orbs.removeChild(this.grid[index].node);
-      delete this.grid[index];
+      this.grid[index] = null;
     } else {
       if (errorIfEmpty) {
         throw new Error(`Position ${index} is already empty.`);
@@ -437,7 +444,7 @@ class Board {
            cx="13.229166"
            fill="url(#radGradSlotBg)" />
       </g>
-    `, { class: 'tile' });
+    `, {class: 'tile'});
   }
 
   /**
@@ -576,7 +583,7 @@ class Rng {
    *
    * @param {Number|null} seed
    */
-  constructor(seed=null) {
+  constructor(seed = null) {
     if (seed === null) {
       seed = +new Date;
     }
@@ -603,44 +610,58 @@ class Rng {
     t ^= t + Math.imul(t ^ t >>> 7, t | 61);
     return ((t ^ t >>> 14) >>> 0) / 4294967296;
   }
+
+  /**
+   * Get next int, inclusive
+   *
+   * @param {Number} max
+   * @return {Number}
+   */
+  nextInt(max) {
+    return Math.floor((max + 1) * this.next());
+  }
 }
 
 class Game {
   /**
    * Init the game
    */
-  constructor() {
+  constructor(seed=null) {
     this.board = new Board();
-    this.rng = new Rng(1);
+    if (seed === null) {
+      seed = +new Date();
+    }
+
+    this.rng = new Rng(seed);
 
     this.layoutTemplates = {
       // templates apparently all have 55 items
 
       //'wheel':     [0,1,2,3,4,5,11,12,13,14,15,16,17,22,23,24,27,28,29,33,34,36,38,40,41,44,45,48,49,52,53,55,56,57,58,59,60,61,62,63,64,65,67,68,71,72,75,76,79,80,82,84,86,87,91,92,93,96,97,98,103,104,105,106,107,108,109,115,116,117,118,119,120],
-      'beyblade':  [0,1,2,3,4,5,12,14,15,23,26,34,35,37,38,39,40,46,47,48,50,51,52,55,58,60,61,64,65,67,68,69,70,71,73,76,79,80,83,84,85,86,87,91,94,95,97,98,103,104,105,106,109,115,120],
+      'beyblade': [0, 1, 2, 3, 4, 5, 12, 14, 15, 23, 26, 34, 35, 37, 38, 39, 40, 46, 47, 48, 50, 51, 52, 55, 58, 60, 61, 64, 65, 67, 68, 69, 70, 71, 73, 76, 79, 80, 83, 84, 85, 86, 87, 91, 94, 95, 97, 98, 103, 104, 105, 106, 109, 115, 120],
-      'tulip':     [4,14,15,16,23,24,25,26,27,28,34,35,36,37,39,40,45,46,47,48,49,50,51,52,56,57,59,60,61,62,63,67,68,69,70,71,72,73,74,80,81,82,83,85,86,93,94,95,96,97,105,106,107,108,109],
+      'tulip': [4, 14, 15, 16, 23, 24, 25, 26, 27, 28, 34, 35, 36, 37, 39, 40, 45, 46, 47, 48, 49, 50, 51, 52, 56, 57, 59, 60, 61, 62, 63, 67, 68, 69, 70, 71, 72, 73, 74, 80, 81, 82, 83, 85, 86, 93, 94, 95, 96, 97, 105, 106, 107, 108, 109],
-      'alien':     [3,4,14,15,16,22,25,26,27,28,34,35,36,37,38,39,40,41,45,46,48,49,51,56,57,58,59,60,61,62,67,68,69,70,71,72,73,74,79,80,81,82,84,85,86,94,95,96,97,98,106,107,108,109,117],
+      'alien': [3, 4, 14, 15, 16, 22, 25, 26, 27, 28, 34, 35, 36, 37, 38, 39, 40, 41, 45, 46, 48, 49, 51, 56, 57, 58, 59, 60, 61, 62, 67, 68, 69, 70, 71, 72, 73, 74, 79, 80, 81, 82, 84, 85, 86, 94, 95, 96, 97, 98, 106, 107, 108, 109, 117],
-      'cube':      [1,5,12,13,14,15,16,17,23,27,29,33,34,35,36,37,38,40,44,48,49,51,52,55,56,57,58,59,60,61,62,64,68,70,71,72,73,75,76,80,82,84,86,92,94,96,97,103,104,105,106,108,118,119,120],
+      'cube': [1, 5, 12, 13, 14, 15, 16, 17, 23, 27, 29, 33, 34, 35, 36, 37, 38, 40, 44, 48, 49, 51, 52, 55, 56, 57, 58, 59, 60, 61, 62, 64, 68, 70, 71, 72, 73, 75, 76, 80, 82, 84, 86, 92, 94, 96, 97, 103, 104, 105, 106, 108, 118, 119, 120],
-      'star':      [3,14,15,22,23,24,25,26,27,34,35,36,37,38,39,40,41,46,47,48,49,50,51,52,57,58,59,60,61,62,63,68,69,70,71,72,73,74,79,80,81,82,83,84,85,86,93,94,95,96,97,98,105,106,117],
+      'star': [3, 14, 15, 22, 23, 24, 25, 26, 27, 34, 35, 36, 37, 38, 39, 40, 41, 46, 47, 48, 49, 50, 51, 52, 57, 58, 59, 60, 61, 62, 63, 68, 69, 70, 71, 72, 73, 74, 79, 80, 81, 82, 83, 84, 85, 86, 93, 94, 95, 96, 97, 98, 105, 106, 117],
-      'flower':    [3,11,12,13,14,15,23,25,27,28,34,36,37,38,39,40,45,46,47,48,49,50,52,53,57,58,59,60,61,62,64,68,70,71,72,73,74,75,79,80,81,82,83,84,86,92,95,96,97,98,104,105,106,107,116],
+      'flower': [3, 11, 12, 13, 14, 15, 23, 25, 27, 28, 34, 36, 37, 38, 39, 40, 45, 46, 47, 48, 49, 50, 52, 53, 57, 58, 59, 60, 61, 62, 64, 68, 70, 71, 72, 73, 74, 75, 79, 80, 81, 82, 83, 84, 86, 92, 95, 96, 97, 98, 104, 105, 106, 107, 116],
-      'windmill':  [4,11,12,13,14,15,16,23,24,25,27,28,34,37,39,40,45,46,47,48,49,50,52,53,56,57,59,60,61,63,64,67,68,70,71,72,73,74,75,80,81,83,86,92,93,95,96,97,104,105,106,107,108,109,116],
+      'windmill': [4, 11, 12, 13, 14, 15, 16, 23, 24, 25, 27, 28, 34, 37, 39, 40, 45, 46, 47, 48, 49, 50, 52, 53, 56, 57, 59, 60, 61, 63, 64, 67, 68, 70, 71, 72, 73, 74, 75, 80, 81, 83, 86, 92, 93, 95, 96, 97, 104, 105, 106, 107, 108, 109, 116],
-      'propeller': [1,2,3,4,13,14,15,16,22,25,28,34,36,37,38,39,40,41,45,46,47,48,50,56,58,60,61,62,67,68,70,71,73,74,75,76,79,80,81,82,83,84,86,87,91,92,95,97,98,103,106,107,108,109,117],
+      'propeller': [1, 2, 3, 4, 13, 14, 15, 16, 22, 25, 28, 34, 36, 37, 38, 39, 40, 41, 45, 46, 47, 48, 50, 56, 58, 60, 61, 62, 67, 68, 70, 71, 73, 74, 75, 76, 79, 80, 81, 82, 83, 84, 86, 87, 91, 92, 95, 97, 98, 103, 106, 107, 108, 109, 117],
-      'garden':    [0,1,2,3,4,5,11,12,13,14,15,16,17,22,23,28,29,33,34,40,41,44,45,52,53,55,56,60,64,65,67,68,75,76,79,80,86,87,91,92,97,98,103,104,105,106,107,108,109,115,116,117,118,119,120],
+      'garden': [0, 1, 2, 3, 4, 5, 11, 12, 13, 14, 15, 16, 17, 22, 23, 28, 29, 33, 34, 40, 41, 44, 45, 52, 53, 55, 56, 60, 64, 65, 67, 68, 75, 76, 79, 80, 86, 87, 91, 92, 97, 98, 103, 104, 105, 106, 107, 108, 109, 115, 116, 117, 118, 119, 120],
-      'windmill2': [1,12,13,14,15,16,17,23,24,26,27,28,34,35,36,37,38,40,44,45,47,50,51,52,56,57,58,60,62,63,64,68,69,70,73,75,76,80,82,83,84,85,86,92,93,94,96,97,103,104,105,106,107,108,119],
+      'windmill2': [1, 12, 13, 14, 15, 16, 17, 23, 24, 26, 27, 28, 34, 35, 36, 37, 38, 40, 44, 45, 47, 50, 51, 52, 56, 57, 58, 60, 62, 63, 64, 68, 69, 70, 73, 75, 76, 80, 82, 83, 84, 85, 86, 92, 93, 94, 96, 97, 103, 104, 105, 106, 107, 108, 119],
-      'bird':      [2,3,4,14,15,25,27,28,29,33,34,35,36,37,38,39,40,45,46,47,48,49,50,51,57,58,59,60,61,62,67,68,70,71,72,73,74,79,80,81,82,83,84,86,87,91,94,95,96,97,98,106,107,109,118],
+      'bird': [2, 3, 4, 14, 15, 25, 27, 28, 29, 33, 34, 35, 36, 37, 38, 39, 40, 45, 46, 47, 48, 49, 50, 51, 57, 58, 59, 60, 61, 62, 67, 68, 70, 71, 72, 73, 74, 79, 80, 81, 82, 83, 84, 86, 87, 91, 94, 95, 96, 97, 98, 106, 107, 109, 118],
-      'strider':   [1,2,3,4,11,12,13,14,15,24,25,26,36,37,38,47,48,49,50,53,58,59,60,61,62,63,64,67,68,69,70,71,72,73,74,75,76,79,80,81,82,83,84,85,86,87,91,92,93,97,98,103,104,109,116],
+      'strider': [1, 2, 3, 4, 11, 12, 13, 14, 15, 24, 25, 26, 36, 37, 38, 47, 48, 49, 50, 53, 58, 59, 60, 61, 62, 63, 64, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 79, 80, 81, 82, 83, 84, 85, 86, 87, 91, 92, 93, 97, 98, 103, 104, 109, 116],
-      'campfire':  [0,1,2,3,4,5,11,15,17,22,23,24,25,26,27,29,33,35,39,41,44,46,51,52,53,55,57,60,63,65,67,68,69,74,76,79,81,85,87,91,93,94,95,96,97,98,103,105,109,115,116,117,118,119,120],
+      'campfire': [0, 1, 2, 3, 4, 5, 11, 15, 17, 22, 23, 24, 25, 26, 27, 29, 33, 35, 39, 41, 44, 46, 51, 52, 53, 55, 57, 60, 63, 65, 67, 68, 69, 74, 76, 79, 81, 85, 87, 91, 93, 94, 95, 96, 97, 98, 103, 105, 109, 115, 116, 117, 118, 119, 120],
-      'skillet':   [0,1,2,5,11,13,17,22,25,26,27,28,29,33,37,39,41,44,45,46,47,48,49,50,53,55,57,59,60,61,65,69,70,71,72,73,74,75,76,81,83,85,87,91,92,95,96,103,107,115,116,117,118,119,120],
+      'skillet': [0, 1, 2, 5, 11, 13, 17, 22, 25, 26, 27, 28, 29, 33, 37, 39, 41, 44, 45, 46, 47, 48, 49, 50, 53, 55, 57, 59, 60, 61, 65, 69, 70, 71, 72, 73, 74, 75, 76, 81, 83, 85, 87, 91, 92, 95, 96, 103, 107, 115, 116, 117, 118, 119, 120],
-      'digger':    [2,3,4,5,16,17,22,27,28,29,33,34,35,36,37,38,39,40,41,44,45,46,47,48,50,51,55,56,57,58,60,61,62,67,70,71,73,79,82,83,84,87,91,94,95,96,98,106,107,108,109,117,118,119,120],
+      'digger': [2, 3, 4, 5, 16, 17, 22, 27, 28, 29, 33, 34, 35, 36, 37, 38, 39, 40, 41, 44, 45, 46, 47, 48, 50, 51, 55, 56, 57, 58, 60, 61, 62, 67, 70, 71, 73, 79, 82, 83, 84, 87, 91, 94, 95, 96, 98, 106, 107, 108, 109, 117, 118, 119, 120],
-      'chestnut':  [3,4,12,13,14,15,16,23,25,27,28,34,36,38,39,40,45,46,47,48,49,50,52,56,57,58,59,60,61,62,64,67,68,71,72,74,75,79,80,81,82,83,84,86,92,95,96,97,98,104,105,106,107,108,109],
+      'chestnut': [3, 4, 12, 13, 14, 15, 16, 23, 25, 27, 28, 34, 36, 38, 39, 40, 45, 46, 47, 48, 49, 50, 52, 56, 57, 58, 59, 60, 61, 62, 64, 67, 68, 71, 72, 74, 75, 79, 80, 81, 82, 83, 84, 86, 92, 95, 96, 97, 98, 104, 105, 106, 107, 108, 109],
-      'manta':     [0,5,11,16,22,23,24,25,26,27,28,29,33,34,35,39,40,44,45,46,47,51,52,56,57,58,59,60,61,62,63,64,68,69,73,74,75,76,80,81,85,86,87,91,92,93,94,95,96,97,98,104,109,115,120],
+      'manta': [0, 5, 11, 16, 22, 23, 24, 25, 26, 27, 28, 29, 33, 34, 35, 39, 40, 44, 45, 46, 47, 51, 52, 56, 57, 58, 59, 60, 61, 62, 63, 64, 68, 69, 73, 74, 75, 76, 80, 81, 85, 86, 87, 91, 92, 93, 94, 95, 96, 97, 98, 104, 109, 115, 120],
-      'pyramids':  [3,4,14,15,16,23,25,26,28,34,35,36,37,38,39,40,45,46,47,48,49,50,51,52,56,58,59,60,61,62,67,68,69,70,71,72,73,74,79,80,81,82,83,84,85,86,94,95,97,98,105,106,107,108,109],
+      'pyramids': [3, 4, 14, 15, 16, 23, 25, 26, 28, 34, 35, 36, 37, 38, 39, 40, 45, 46, 47, 48, 49, 50, 51, 52, 56, 58, 59, 60, 61, 62, 67, 68, 69, 70, 71, 72, 73, 74, 79, 80, 81, 82, 83, 84, 85, 86, 94, 95, 97, 98, 105, 106, 107, 108, 109],
-      'bigwheel':  [0,1,2,3,4,5,11,13,17,22,25,28,29,33,36,37,38,39,41,44,45,46,47,50,53,55,58,60,62,65,67,70,73,74,75,76,79,81,82,83,84,87,91,92,95,98,103,107,109,115,116,117,118,119,120],
+      'bigwheel': [0, 1, 2, 3, 4, 5, 11, 13, 17, 22, 25, 28, 29, 33, 36, 37, 38, 39, 41, 44, 45, 46, 47, 50, 53, 55, 58, 60, 62, 65, 67, 70, 73, 74, 75, 76, 79, 81, 82, 83, 84, 87, 91, 92, 95, 98, 103, 107, 109, 115, 116, 117, 118, 119, 120],
-      'handshake': [0,1,2,3,4,5,11,12,13,15,16,22,23,24,25,27,33,34,35,36,38,46,48,49,50,58,59,60,61,62,70,71,72,74,82,84,85,86,87,93,95,96,97,98,104,105,107,108,109,115,116,117,118,119,120],
+      'handshake': [0, 1, 2, 3, 4, 5, 11, 12, 13, 15, 16, 22, 23, 24, 25, 27, 33, 34, 35, 36, 38, 46, 48, 49, 50, 58, 59, 60, 61, 62, 70, 71, 72, 74, 82, 84, 85, 86, 87, 93, 95, 96, 97, 98, 104, 105, 107, 108, 109, 115, 116, 117, 118, 119, 120],
-      'thinwheel': [0,1,2,3,4,5,11,12,16,17,22,24,27,29,33,36,38,41,44,48,49,53,55,56,57,58,59,60,61,62,63,64,65,67,71,72,76,79,82,84,87,91,93,96,98,103,104,108,109,115,116,117,118,119,120],
+      'thinwheel': [0, 1, 2, 3, 4, 5, 11, 12, 16, 17, 22, 24, 27, 29, 33, 36, 38, 41, 44, 48, 49, 53, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 67, 71, 72, 76, 79, 82, 84, 87, 91, 93, 96, 98, 103, 104, 108, 109, 115, 116, 117, 118, 119, 120],
-      'heavywheel':[12,13,14,15,16,23,24,25,27,28,34,36,37,38,39,40,45,46,47,48,49,50,52,56,57,58,59,60,61,62,63,64,68,70,71,72,73,74,75,80,81,82,83,84,86,92,93,95,96,97,104,105,106,107,108],
+      'heavywheel': [12, 13, 14, 15, 16, 23, 24, 25, 27, 28, 34, 36, 37, 38, 39, 40, 45, 46, 47, 48, 49, 50, 52, 56, 57, 58, 59, 60, 61, 62, 63, 64, 68, 70, 71, 72, 73, 74, 75, 80, 81, 82, 83, 84, 86, 92, 93, 95, 96, 97, 104, 105, 106, 107, 108],
-      'virus':     [2,3,13,14,15,22,24,26,27,34,35,36,37,38,39,40,41,46,47,48,49,50,51,57,58,59,60,61,62,63,68,69,70,71,72,73,75,79,80,82,83,84,85,86,87,91,92,93,94,95,96,97,98,106,117],
+      'virus': [2, 3, 13, 14, 15, 22, 24, 26, 27, 34, 35, 36, 37, 38, 39, 40, 41, 46, 47, 48, 49, 50, 51, 57, 58, 59, 60, 61, 62, 63, 68, 69, 70, 71, 72, 73, 75, 79, 80, 82, 83, 84, 85, 86, 87, 91, 92, 93, 94, 95, 96, 97, 98, 106, 117],
-      'frisbee':   [0,11,12,13,14,15,22,25,26,27,28,29,33,34,36,38,39,40,41,45,46,47,49,50,53,57,58,59,60,62,64,65,68,69,72,74,75,80,81,82,83,84,85,86,92,95,96,97,104,106,107,115,116,117,118],
+      'frisbee': [0, 11, 12, 13, 14, 15, 22, 25, 26, 27, 28, 29, 33, 34, 36, 38, 39, 40, 41, 45, 46, 47, 49, 50, 53, 57, 58, 59, 60, 62, 64, 65, 68, 69, 72, 74, 75, 80, 81, 82, 83, 84, 85, 86, 92, 95, 96, 97, 104, 106, 107, 115, 116, 117, 118],
     };
 
     this.newGame()
@@ -720,7 +741,7 @@ class Game {
     return tpl
       .sort((a, b) => a - b)
       .map((n) => {
-        let { x, y } = this.board.gridIndexToXy(n);
+        let {x, y} = this.board.gridIndexToXy(n);
         return this.board.xyToGridIndex(5 + y - x, y);
       })
       .sort((a, b) => a - b);
@@ -767,9 +788,13 @@ class Game {
   }
 
   isAvailable(n) {
+    return this.getNeighbours(n).freeSequence >= 3;
+  }
+
+  getNeighbours(n) {
     let {x, y} = this.board.gridIndexToXy(n);
 
-    let neighbors = [
+    let freeSpaces = [
       this.isOutside(x - 1, y) || !this.board.grid[n - 1],
       this.isOutside(x - 1, y - 1) || !this.board.grid[n - 12],
       this.isOutside(x, y - 1) || !this.board.grid[n - 11],
@@ -778,235 +803,246 @@ class Game {
       this.isOutside(x, y + 1) || !this.board.grid[n + 11],
     ];
 
-    neighbors.push(neighbors[0]);
+    let nOccupied = 0;
-    neighbors.push(neighbors[1]);
+    for (let i = 0; i < 6; i++) {
+      if (!freeSpaces[i]) {
+        nOccupied++;
+      }
+    }
+
+    // if(this.debuggetneigh) console.log(`${x}×${y} #${n}, nocc ${nOccupied} `+JSON.stringify(freeSpaces));
 
-    let conseq = 0;
+    let freeSequence = 0;
-    for (let i = 0; i < neighbors.length; i++) {
+    let maxFreeSequence = 0;
-      if (neighbors[i]) {
+    for (let i = 0; i < 12; i++) {
-        conseq++;
+      if (freeSpaces[i % 6]) {
-        if (conseq === 3) {
+        freeSequence++;
-          return true;
+        if (freeSequence >= 6) {
+          maxFreeSequence = freeSequence;
+          break;
+        }
+        if (freeSequence > maxFreeSequence) {
+          maxFreeSequence = freeSequence;
         }
       } else {
-        conseq = 0;
+        freeSequence = 0;
       }
     }
 
-    return false;
+    return {neighbours: nOccupied, freeSequence: maxFreeSequence};
   }
 
-  placeOrbs() {
+  placeOrbs(template) {
     this.board.removeAllOrbs();
 
-    let template = this.getRandomTemplate();
     let allowed = [];
-    for(let i = 0; i <= 120; i++) {
+    for (let i = 0; i <= 120; i++) {
-      allowed.push(template.includes(i));
+      let allo = template.includes(i);
-      if (!template.includes(i)) {
+      allowed.push(allo);
+
+      // Highlight pattern shape
+
       if (this.board.tiles[i]) {
-          this.board.$bg.removeChild(this.board.tiles[i])
+        if (allo) {
+          this.board.tiles[i].setAttribute('opacity', 1)
+        } else {
+          this.board.tiles[i].setAttribute('opacity', 0.6)
         }
       }
     }
 
-    let place = (n, symbol) => {
+    const place = (n, symbol) => {
       if (!allowed[n]) throw Error(`Position ${n} not allowed by template`);
       if (this.board.grid[n]) throw Error(`Position ${n} is occupied`);
       this.board.placeOrbByIndex(n, symbol);
     };
 
-    let findAvailableIndex = () => {
+    const findAvailableIndexWithNeighbours = (count) => {
       let candidates = [];
-      for(let i=0; i<template.length;i++) {
+      for (let i = 0; i < template.length; i++) {
-        let n = template[i];
+        const n = template[i];
-        if (!this.board.grid[n] && this.isAvailable(n)) {
+        const neigh = this.getNeighbours(n);
+        // console.log(neigh);
+        if (!this.board.grid[n] && neigh.neighbours === count && neigh.freeSequence >= 3) {
           candidates.push(n);
         }
       }
 
       if (candidates.length) {
-        return candidates[Math.floor(this.rng.next()*candidates.length)]
+        return candidates[Math.floor(this.rng.next() * candidates.length)]
       } else {
-        throw Error("Failed to find available tile");
+        return false;
       }
     };
 
-    try {
+    const findAvailableIndex = () => {
+      for (let i = 6; i >= 0; i--) {
+        const n = findAvailableIndexWithNeighbours(i);
+        if (n !== false) return n;
+      }
 
-      place(60, 'gold');
+      throw Error("Failed to find available tile");
+    };
 
-      let toPlace = [
+    place(60, 'gold');
-        // gold is placed always to 60 (5x5)
-        ['salt', 'salt'],
-        ['salt', 'salt'],
-        ['mors', 'vitae'],
-        ['mors', 'vitae'],
-        ['mors', 'vitae'],
-        ['mors', 'vitae'],
-        ['air', 'air'],
-        ['air', 'air'],
-        ['air', 'air'],
-        ['air', 'air'],
-        ['fire', 'fire'],
-        ['fire', 'fire'],
-        ['fire', 'fire'],
-        ['fire', 'fire'],
-        ['water', 'water'],
-        ['water', 'water'],
-        ['water', 'water'],
-        ['water', 'water'],
-        ['earth', 'earth'],
-        ['earth', 'earth'],
-        ['earth', 'earth'],
-        ['earth', 'earth'],
-        ['lead', 'mercury'],
-        ['tin', 'mercury'],
-        ['iron', 'mercury'],
-        ['copper', 'mercury'],
-        ['silver', 'mercury'],
-      ];
 
-      let shuffle = (a) => {
+    const toPlace = this.buildPlacementList();
-        let j, x, i;
-        for (i = a.length - 1; i > 0; i--) {
-          j = Math.floor(this.rng.next() * (i + 1));
-          x = a[i];
-          a[i] = a[j];
-          a[j] = x;
-        }
-        return a;
-      };
 
-      shuffle(toPlace);
+    // unpack the pairs
-      toPlace = toPlace.reduce((a,c) => {
+    let toPlace_stack = toPlace.reduce((a, c) => {
       a.push(c[0]);
       a.push(c[1]);
       return a;
     }, []);
 
-      console.log(toPlace);
+    while (toPlace_stack.length > 0) {
-
+      place(findAvailableIndex(), toPlace_stack.pop())
-      let history = [];
+    }
-
-      const maxiter = 1000;
-      for (let itern = 0; itern < maxiter && toPlace.length > 0; itern++) {
-        console.log('--- main iteration -----------');
-
-        let symbol = toPlace.pop();
-        console.log('take ' + symbol);
-
-        try {
-          console.log('?place ' + symbol);
-          let index = findAvailableIndex();
-          place(index, symbol);
-          console.log('placed ' + symbol + ' to ' + index);
-          history.push({symbol, index});
-        } catch (e) {
-          toPlace.push(symbol);
-          console.log('*return unplaced ' + symbol);
-
-          console.log('BACKTRACK----------- failed to place ' + symbol);
-          console.log('toPlace=',toPlace);
-          console.log('history=',history);
-
-          let depth = Math.min(1, history.length);
-          let backtracking = true;
-
-          // let retryAtThisLevel=0;
-          while (backtracking) {
-            // if (retryAtThisLevel > 0) {
-            //   retryAtThisLevel = 0;
-            //   depth++;
-            //   console.log(`DEEPER`);
-            // } else {
-            //   retryAtThisLevel++;
-            // }
 
-            console.log('>>> Attempt backtrack of depth ' + depth);
+    console.info("Found a valid board!");
 
-            for (let j = 0; j < depth; j++) {
+    console.log('Solution: ', toPlace);
-              let hist = history.pop();
-              this.board.removeOrbByIndex(hist.index, true);
-              toPlace.push(hist.symbol);
-              console.log('undo & return (hist) ' + hist.symbol + ' at ' + hist.index)
   }
 
-            console.log(`try getting back ${depth + 1} steps`);
+  updateOrbDisabledStatus() {
-            let successes = 0;
+    for (let n = 0; n < 120; n++) {
-            for (let j = 0; j <= depth; j++) {
+      if (this.board.grid[n]) {
-              let symbol = toPlace.pop();
+        this.board.grid[n].node.classList.toggle('disabled', !this.isAvailable(n));
-              console.log('take ' + symbol);
+      }
-
+    }
-              itern++;
-              if (itern > maxiter) {
-                throw Error("Exceeded max iteration depth");
   }
 
+  newGame() {
+    // this.board.onTileClick = (n) => {
+    //   console.log(n, this.board.gridIndexToXy(n));
+    // };
+
+    const RETRY_IN_TEMPLATE = 100;
+    const RETRY_NEW_TEMPLATE = 15;
+
+    // retry loop, should not be needed if everything is correct
+    let suc = false;
+    let numretries = 0;
+    const alertOnError = false;
+    for (let i = 0; i < RETRY_NEW_TEMPLATE && !suc; i++) {
+      console.log('RNG seed is: ' + this.rng.state);
+      const template = this.getRandomTemplate();
+      for (let j = 0; j < RETRY_IN_TEMPLATE; j++) {
         try {
-                console.log('?place ' + symbol);
+          this.placeOrbs(template);
-                let index = findAvailableIndex();
+          suc = true;
-                place(index, symbol);
-                history.push({symbol, index});
-                console.log('placed ' + symbol + ' to ' + index);
-
-                if (j === depth) {
-                  console.log('Backtracking success');
-                  backtracking = false;
           break;
-                }
-
-                successes++;
         } catch (e) {
-                console.log(`backtrack of depth ${depth} fail`);
+          if (alertOnError) alert('welp');
-
+          numretries++;
-                toPlace.push(symbol);
+          console.warn(e.message);
-                console.log('return unplaced ' + symbol);
-
-                // for(let k = 0; k < successes; k++) {
-                //   let hist = history.pop();
-                //   this.board.removeOrbByIndex(hist.index, true);
-                //   toPlace.push(hist.symbol);
-                //   console.log('undo & return (hist) ' + hist.symbol + ' at ' + hist.index);
-                // }
-
-                console.log(`DEEPER`);
-                depth++;
-                break;
         }
       }
+      if (!suc) {
+        console.warn("Exhausted all retries for the template, getting a new one");
+      }
     }
 
-          console.log('end of backtrack loop, toPlace=', toPlace);
+    if (!suc) {
-          console.log('history=',history);
+      alert(`Sorry, could not find a valid board setup after ${numretries} retries.`);
+      return;
+    } else {
+      console.info(`Found valid solution (with ${numretries} retries)`);
     }
+
+    this.updateOrbDisabledStatus()
   }
 
-      if (toPlace.length > 0) {
+  shuffleArray(a) {
-        throw Error("Failed to place some symbols: " + JSON.stringify(toPlace));
+    let j, x, i;
+    for (i = a.length - 1; i > 0; i--) {
+      j = this.rng.nextInt(i);
+      x = a[i];
+      a[i] = a[j];
+      a[j] = x;
+    }
+    return a;
   }
 
-      //place(findAvailableIndex(), metals.pop());
+  buildPlacementList() {
+    let toPlace = [
+      ['air', 'air'],
+      ['air', 'air'],
+      ['air', 'air'],
+      ['air', 'air'],
 
-    } catch (e) {
+      ['fire', 'fire'],
-      console.error(e)
+      ['fire', 'fire'],
+      ['fire', 'fire'],
+      ['fire', 'fire'],
+
+      ['water', 'water'],
+      ['water', 'water'],
+      ['water', 'water'],
+      ['water', 'water'],
+
+      ['earth', 'earth'],
+      ['earth', 'earth'],
+      ['earth', 'earth'],
+      ['earth', 'earth'],
+    ];
 
-      for(let i=0;i<120;i++) {
+    let newSaltedPairs = [];
-        if (!this.board.grid[i] && allowed[i]) {
+    const nsalted = this.rng.nextInt(2);
-          console.log('Free cell '+i+' -> isAvail? '+this.isAvailable(i), this.board.gridIndexToXy(i));
+    for (let i = 0; i < nsalted; i++) {
+      while (true) {
+        const n = this.rng.nextInt(toPlace.length-1);
+        if (toPlace[n][1] !== 'salt') {
+          // console.log(`Pairing ${toPlace[n][1]} with salt.`);
+          newSaltedPairs.push([toPlace[n][1], 'salt']);
+          toPlace[n][1] = 'salt';
+          break;
         }
       }
     }
+    toPlace = toPlace.concat(newSaltedPairs);
+    // if we have some salt pairs left
+    for (let i = 0; i < 2 - nsalted; i++) {
+      toPlace.push(['salt', 'salt']);
     }
 
-  newGame() {
+    // these are always paired like this, and don't support salt
-    //
+    toPlace = toPlace.concat([
+      ['mors', 'vitae'],
+      ['mors', 'vitae'],
+      ['mors', 'vitae'],
+      ['mors', 'vitae'],
+    ]);
 
-    this.board.onTileClick = (n) => {
+    // shuffle the pairs that have random order (i.e. not metals)
-      console.log(n, this.board.gridIndexToXy(n));
+    this.shuffleArray(toPlace);
-    };
+
+
+    // the order here is actually significant, so let's pay attention...
+    const metals = [
+      ['lead', 'mercury'],
+      ['tin', 'mercury'],
+      ['iron', 'mercury'],
+      ['copper', 'mercury'],
+      ['silver', 'mercury'],
+    ];
+    let mPos = [];
+    for (let i = 0; i < metals.length; i++) {
+      let x;
+      // find a unique position
+      do {
+        x = this.rng.nextInt(toPlace.length + i);
+      } while (mPos.includes(x));
+      mPos.push(x)
+    }
+    mPos.sort((a, b) => a - b);
+    // console.log('Metal positions ', mPos);
+    // inject them into the array
+    metals.forEach((pair, i) => {
+      toPlace.splice(mPos[i] + i, 0, pair);
+    });
 
-    this.placeOrbs()
+    return toPlace;
   }
 }