new builder heuristic based on distance from center + - some difficulty margin

script.js

@@ -742,8 +742,9 @@ class SettingsStorage {
       version: 1,
       log: 'info',
       allowTemplateAugmenting: false,
-      retryTemplate: 30,
-      attemptTemplates: 50,
+      retryTemplate: 120,
+      attemptTemplates: 20,
+      difficulty: 35,
       svgEffects: false,
       dimBlocked: true,
       logSolution: false,
@@ -1140,7 +1141,13 @@ class Game {
       }
     }
 
-    return {neighbours: nOccupied, freeSequence: maxFreeSequence};
+    let { rx, ry } = this.board.gridXyToCoord(x, y);
+
+    return {
+      neighbours: nOccupied,
+      freeSequence: maxFreeSequence,
+      centerWeight: Math.round(Math.sqrt(Math.pow(rx, 2) + Math.pow(ry, 2))),
+    };
   }
 
   placeOrbs(template) {
@@ -1183,31 +1190,48 @@ class Game {
       this.board.grid[n] = null;
     };
 
-    const findAvailableIndexWithNeighbours = (count, except = null) => {
+    const findBestCandidate = (except = null) => {
       let candidates = [];
       for (let n of template) {
         if (except && except.includes(n)) continue;
 
         if (!this.board.grid[n]) {
+          // is free
           const neigh = this.getNeighbours(n);
-          if (neigh.neighbours === count && neigh.freeSequence >= 3) {
-            candidates.push(n);
+          if (neigh.freeSequence >= 3) {
+            candidates.push({
+              n,
+              cw: neigh.centerWeight
+            });
           }
         }
       }
 
+      candidates.sort((a, b) => a.cw - b.cw);
+
       if (candidates.length) {
-        return this.arrayChoose(candidates)
-      } else {
-        return false;
+        // return candidates[0].n;
+        let top = [];
+        let topw = candidates[0].cw;
+        for(let cand of candidates) {
+          if (cand.cw <= topw + this.cfg.difficulty) { // TODO this could vary by template
+            top.push(cand);
+          }
+        }
+
+        //the neighbor count is not used for anything anymore, oops
+
+        // console.log('Got a choice of '+top.length+' tiles');
+
+        return this.arrayChoose(top).n;
       }
+
+      return false;
     };
 
     const findAvailableIndex = (except = null) => {
-      for (let i = 6; i >= 0; i--) {
-        const n = findAvailableIndexWithNeighbours(i, except);
-        if (n !== false) return n;
-      }
+      const n = findBestCandidate(except);
+      if (n !== false) return n;
 
       // this corrupts the template, but makes the likelihood of quickly finding a valid solution much higher.
       if (template.length !== BOARD_SIZE && this.cfg.allowTemplateAugmenting) {