diff --git a/index.html b/index.html
index 3e8cdc9..0917537 100644
--- a/index.html
+++ b/index.html
@@ -846,7 +846,23 @@ <h1>Batch Card Printer</h1>
                     [/^cs(\d+)-(\d+)$/gi, (match)=>{
                         let arr = this.randomize_array(match[2], parseInt(match[1]));
                         return arr.slice(0, 25);
-                    }]
+                    }],
+                    [/^csb(\d+)-(\d+)$/gi, (match=>{
+                        let arr = this.randomize_array(match[2], parseInt(match[1]));
+                        // an extra array for number that exceed the grouping length
+                        // grouping length is gotten by dividing the total number by 5
+                        // and dropping the remainder.
+                        //
+                        // eg: in normal bingo 76 would be outside of the b i n g o
+                        //     groups, it should overflow into group b
+                        let groups = Array(6).fill().map(()=>[]);
+                        let group_range = Math.floor(arr.length/5);
+                        arr.forEach((num, i)=>groups[Math.floor(num/group_range)].push(num))
+                        // excess numbers to be distributed
+                        groups[5].forEach((num, i)=>groups[i].push(num))
+                        delete groups[5]
+                        return this.arr_2d_flip(groups.map((x)=>x.slice(0,5)).flat(), 5)
+                    })]
                 ],
 
                 to_arrays: function (c){return function* _(){