diff --git a/package-lock.json b/package-lock.json
index 0582eab..726980c 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -23,7 +23,6 @@
 				"prettier": "^3.1.1",
 				"prettier-plugin-svelte": "^3.1.2",
 				"svelte": "^4.2.7",
-				"svelte-popover": "^2.0.8",
 				"vite": "^5.0.3",
 				"vitest": "^2.0.0"
 			}
@@ -3112,13 +3111,6 @@
 				"svelte": "^3.19.0 || ^4.0.0"
 			}
 		},
-		"node_modules/svelte-popover": {
-			"version": "2.0.8",
-			"resolved": "https://registry.npmjs.org/svelte-popover/-/svelte-popover-2.0.8.tgz",
-			"integrity": "sha512-Yvz4FpvvXc5aBGyIE/TlGlqULLKkcfc7N0MoaqNXHMRVXxla+sc7G1xSCCURP3VqP0nZ5cIyPWOLLWFXuJjTRA==",
-			"dev": true,
-			"license": "ISC"
-		},
 		"node_modules/svelte-preprocess": {
 			"version": "6.0.2",
 			"resolved": "https://registry.npmjs.org/svelte-preprocess/-/svelte-preprocess-6.0.2.tgz",
diff --git a/package.json b/package.json
index 7c8dcdc..a8e66a4 100644
--- a/package.json
+++ b/package.json
@@ -22,7 +22,6 @@
 		"prettier": "^3.1.1",
 		"prettier-plugin-svelte": "^3.1.2",
 		"svelte": "^4.2.7",
-		"svelte-popover": "^2.0.8",
 		"vite": "^5.0.3",
 		"vitest": "^2.0.0"
 	},
diff --git a/src/routes/+page.svelte b/src/routes/+page.svelte
index 9bcb3c5..f346f86 100644
--- a/src/routes/+page.svelte
+++ b/src/routes/+page.svelte
@@ -1,14 +1,12 @@
 <script>
+    // get the data from the JSON Webservices feed in +page.js
     export let data;
     const { webservices } = data;
 
-    //console.log('orig:', webservices);
-    //console.log('orig affiliates:', webservices.affiliates);
-    //console.log('orig hosts:', webservices.hosts);
-
     // source: https://mokole.com/palette.html 20 colors with default settings otherwise
     const colours30 = [ "#808080", "#7f0000", "#006400", "#808000", "#483d8b", "#008b8b", "#cd853f", "#00008b", "#7f007f", "#8fbc8f", "#b03060", "#ff0000", "#ff8c00", "#00ff00", "#9400d3", "#00ff7f", "#dc143c", "#00ffff", "#00bfff", "#0000ff", "#f08080", "#adff2f", "#1e90ff", "#ffff54", "#90ee90", "#add8e6", "#ff1493", "#7b68ee", "#ee82ee", "#ffe4b5" ];
 
+    // digest and return useful info from the Webservices JSON feed
     function processData(webservices) {
         let instances = 0;
         let current = [];
@@ -96,12 +94,6 @@
                // affiliate_data[key] = affiliate;
            // }
         }
-        //console.log('categories: ', categories);
-        //console.log('analogues: ', analogues);
-        //console.log('licenses: ', licenses);
-        //console.log('statuses: ', statuses);
-        //console.log('affiliates: ', affiliates);
-        //console.log('hosts: ', hosts);
 
         return {
             total_instances: instances,
@@ -123,11 +115,13 @@
     }
 
 //    console.log(technologies);
+    // return true if a tech object includes valid instances
     function hasInstances(tech) {
         if (tech.hasOwnProperty('instances') && tech.instances.constructor === Array && tech.instances.length) return true;
         return false;
     }
 
+    // return an array of keys from an object
     function getKeys(ob) {
         let keys = [];
         for (let key in ob) {
@@ -136,14 +130,37 @@
         return keys;
     }
 
+    // get intersection: ref https://bobbyhadz.com/blog/javascript-get-intersection-of-two-arrays
+    function getIntersection(a, b) {
+        const set1 = new Set(a);
+        const set2 = new Set(b);
+
+        const intersection = [...set1].filter(
+            element => set2.has(element)
+        );
+
+        return intersection;
+    }
+
+    // combine an array of terms into a sentence with proper Oxford commas, dealing with the special cases
+    // of one or two elements.
     function toOxfordCommaString(arr) {
         if (arr.length == 1) return arr;
+        if (arr.length == 2) return arr.join(' and ');
         else {
             var last = arr.pop();
             return arr.join(', ') + ', and ' + last;
         }
     }
 
+    // return a singular or plural term depending on the value of 'count'
+    function pluraliser(singular, plural, count) {
+        if (count > 1) return plural;
+        return singular;
+    }
+
+    // assign colours from a set of differentiated colours to a list of tags...
+    // this one is for 'hosts'
     function hostColours(host_list, colours, hosts) {
         let host_array = {};
         let i = 0;
@@ -163,31 +180,76 @@
         return host_array;
     }
 
+    // assign colours from a set of differentiated colours to a list of tags...
+    // this one is for 'affiliates'
     function affiliateColours(affiliate_list, colours, affiliates) {
-        let affiliate_array = {};
+        let affiliate_result = {};
         let i = 0;
 
         //console.log('affiliates:', affiliates);
+        console.log('affiliate_list:', affiliate_list);
 
         for (const affiliate of affiliate_list) {
             //console.log('affiliate:', affiliate);
             if (affiliates[affiliate].hasOwnProperty('name') && affiliates[affiliate].hasOwnProperty('website')) {
-                affiliate_array[affiliate] = {
+                affiliate_result[affiliate] = {
                     "colour": colours[i++],
                     "name": affiliates[affiliate].name,
                     "website": affiliates[affiliate].website
                 }
             }
         }
-        return affiliate_array;
+        return affiliate_result;
     }
 
+    // sort technologies alphabetically by name
+    function sortTechnologies(technologies) {
+        return technologies.sort((a,b) => a.name.localeCompare(b.name));
+    }
+
+    // generic function to find the intersection of two arrays
+    // approach ref: https://bobbyhadz.com/blog/javascript-get-intersection-of-two-arrays
+    function inCommon(a, b) {
+        const set1 = new Set(a);
+        const set2 = new Set(b);
+
+        const intersection = [...set1].filter(
+            element => set2.has(element)
+        );
+        console.log('intersection = ', intersection);
+        return intersection;
+    }
+
+    // filter technologies based on a list of Categories
+    function filterTechnologiesByCategoryList(technologies, list) {
+        console.log('looking for tech in categories: ', list);
+        const included = [];
+        technologies.forEach(function(tech, index) {
+            //console.log('tech(' + index + '): ', tech);
+            if (hasInstances(tech)) {
+                const intersection = inCommon(tech.categories, list);
+                console.log('categories: ', tech.categories);
+                //console.log('list: ', list);
+                console.log('intersection: ', intersection);
+                if (intersection && intersection.constructor === Array) {
+                    //console.log('intersection length: '. intersection.length);
+                    if (intersection.length > 0) {
+                        console.log('including tech: ', tech);
+                        included.push(tech);
+                    }
+                } else {
+                    console.log('intersection not array');
+                }
+            }
+        });
+        console.log('found ' + included.length + ' technologies.')
+        return included;
+    }
 
     const results = processData(webservices);
     //console.log('results: ', results);
 
     //const technologies = webservices.technologies;
-    const technologies = results.active_services;
     //console.log(technologies);
 
     const category_list = getKeys(results.tech_lists.category_list).sort();
@@ -203,12 +265,127 @@
     //console.log('affiliate_data: ', results.affiliates);
     const host_colours = hostColours(host_list, colours30, hosts);
     //console.log('host_colours:', host_colours);
+    colours30.sort();
     const affiliate_colours = affiliateColours(affiliate_list, colours30, affiliates);
     //console.log('affiliate_colours:',affiliate_colours);
 
     //console.log('categories array: ', results.tech_tags.categories);
     //console.log('categories keys: ', categories);
 
+    console.log('category_list: ', category_list);
+    //console.log('analogue_list: ', analogue_list);
+    console.log('license_list: ', license_list);
+    console.log('status_list: ', status_list);
+    console.log('affiliate_list: ', affiliate_list);
+    console.log('hosts_list: ', host_list);
+
+            // filter technolologies based on a subset of categories
+    const full_category_list = [
+        'App Ecosystem',
+        'Application Design',
+        'Asset Management',
+        'Association Management',
+        'Association Management System',
+        'Blog Syndication',
+        'Book Reviews',
+        'Calendar',
+        'Collaborative',
+        'Collaborative Markdown Editing',
+        'Collaborative Wiki',
+        'Content Management Systems',
+        'Digital Media Sales',
+        'Document Management',
+        'Email Marketing Automation',
+        'Email Services',
+        'Enterprise Resource Planning',
+        'Event Management',
+        'Facial Recognition',
+        'Facility Booking',
+        'Federated Messaging',
+        'Fediverse',
+        'File Synchronisation',
+        'Forum',
+        'Framasoft',
+        'Home Automation',
+        'Home Security',
+        'Image Backup',
+        'Image Gallery',
+        'Kanban Project Management',
+        'Learning Management System',
+        'Link Ranking',
+        'Link Sharing',
+        'Link Shortener',
+        'Membership Management',
+        'Messaging Cache',
+        'Micro-blogging',
+        'Multi-Domain Server',
+        'Multimedia',
+        'Music Discovery',
+        'Music Streaming',
+        'Network Infrastructure Monitoring',
+        'Newsletters',
+        'Online Forms',
+        'Password Manager',
+        'Photos',
+        'Portfolio Management',
+        'Privacy',
+        'Productivity',
+        'Reading List',
+        'Remote Desktop Sharing',
+        'Remote Incremental Encrypted System Backups',
+        'Reverse Proxy',
+        'Rich Messaging Client',
+        'Rich Messaging Server',
+        'Scheduling',
+        'Server Monitoring',
+        'Share Secrets Management',
+        'Single Sign-On',
+        'Social Bookmarking',
+        'Social Media',
+        'Software Development Forge',
+        'Software Interface Designer',
+        'Streaming',
+        'Surveys',
+        'TURN/STUN Server',
+        'Video',
+        'Video Conferencing',
+        'Video Surveillance',
+        'Visualisation of Time Series Data',
+        'Webmail',
+        'Webserver',
+        'Website Analytics'
+    ];
+    const copyleft_list = [
+        'AGPL-3',
+        'AGPL-3+',
+        'GPL',
+        'GPL-2',
+        'GPL-2+',
+        'GPL-3',
+        'GPL-3+',
+        'LGPL-3',
+    ];
+    const category_filter_list = [
+        'Fediverse',
+        'Social Media',
+        'Software Development Forge',
+        'Software Interface Designer',
+        'Streaming',
+        'Surveys',
+        'TURN/STUN Server',
+        'Video',
+        'Video Conferencing',
+        'Video Surveillance',
+        'Visualisation of Time Series Data',
+        'Webmail',
+        'Webserver',
+        'Website Analytics'
+    ];
+
+    const filtered_technologies = filterTechnologiesByCategoryList(results.active_services, category_filter_list);
+    const technologies = sortTechnologies(filtered_technologies);
+
+
 </script>
 
 <div class="webservices">
@@ -231,10 +408,15 @@
         </div>
     </div>
     <div class="tiles">
-        {#each technologies as technology}
+        {#each filtered_technologies as technology}
         <div class="tile technology">
+            <div class="links">
+                {#if (technology.repository)}<span class="repository"><a href="{technology.repository}" title="The source code repository for {technology.name}">R</a></span>{/if}
+                {#if (technology.wikipedia)}<span class="wikipedia"><a href="{technology.wikipedia}" title="Wikipedia Page for {technology.name}">W</a></span>{/if}
+            </div>
             <h2><a href="{technology.website}">{technology.name}</a></h2>
             {#if (technology.license)}<p class="license" title="The libre license for this project is {technology.license}">License: <span class="value">{technology.license}</span></p>{/if}
+            {#if (technology.categories)}<p class="categories">{pluraliser('Category','Categories',technology.categories.length)}: <span class="value">{toOxfordCommaString(technology.categories)}</span></p>{/if}
             {#if (technology.analogues)}<p class="analogues">Alternative to <span class="value">{toOxfordCommaString(technology.analogues)}</span></p>{/if}
             <p class="description">{technology.description}</p>
             {#if hasInstances(technology)}
@@ -310,12 +492,12 @@
     .tiles {
         display: grid;
         grid-gap: 15px;
-        grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
+        grid-template-columns: repeat(auto-fit, minmax(270px, 1fr));
     }
     /* flip card stuff: https://www.w3schools.com/howto/howto_css_flip_card.asp */
     .tile {
-        height: 400px;
-        min-width: 250px;
+        height: 500px;
+        min-width: 270px;
         max-width: 400px;
         overflow: hidden;
         box-sizing: border-box;
@@ -324,7 +506,18 @@
         text-overflow: ellipsis;
         overflow: hidden;
         position: relative;
+        background-color: #eee;
     }
+    .tile .links {
+        position: absolute;
+        top: 0;
+        right: 0;
+        padding: 2px 6px;
+        font-size: 90%;
+    }
+    .tile .links a { color: #e6c4fc; }
+    .tile .links a:visited { color: #ced0ff; }
+    .tile .links a:hover { color: #fff; }
     .tile h2 {
         background-color: #999;
         text-align: center;
@@ -335,7 +528,7 @@
     .tile h2 a:visited { color: #ced0ff; }
     .tile h2 a:hover { color: #fff; }
     .tile .description {
-        height: 200px;
+        height: 260px;
         text-overflow: ellipsis;
         overflow: hidden;
     }
@@ -345,7 +538,7 @@
         color: #555;
     }
     .instances {
-        background-color: #eee;
+        background-color: #ddd;
         position: absolute;
         bottom: 0;
         height: 3em;
@@ -357,14 +550,14 @@
     .webservices li { list-style-type: none; }
     .value { font-weight: bold; color: #000; }
     .marker { vertical-align: middle; }
-    .triangle {
+   /* .triangle {
         --side-size: 20px;
         border-left: var(--side-size) solid transparent;
         border-right: var(--side-size) solid transparent;
         border-bottom: calc(2 * var(--side-size) * 0.866) solid green;
         border-top: var(--side-size) solid transparent;
         display: inline-block;
-    }
+    }*/
     .circle {
         height: 20px;
         width: 20px;