diff --git a/elfeed-summary.el b/elfeed-summary.el
index a23b631..666c0cd 100644
--- a/elfeed-summary.el
+++ b/elfeed-summary.el
@@ -37,6 +37,7 @@
   :offset 4
   :tag "Extract subset of elfeed feed list"
   :type '(choice (symbol :tag "One tag")
+                 (const :tag "All" :all)
                  (cons :tag "Match title"
                        (const :tag "Title" title)
                        (choice (string :tag "String")
@@ -52,6 +53,9 @@
                  (cons :tag "AND"
                        (const :tag "AND" and)
                        (repeat elfeed-summary-query))
+                 (cons :tag "NOT"
+                       (const :tag "NOT" not)
+                       elfeed-summary-query)
                  (repeat :tag "OR (Implicit)" elfeed-summary-query)
                  (cons :tag "OR"
                        (const :tag "OR" or)
@@ -63,39 +67,106 @@
   :tag "Group"
   :type '(repeat
           (choice
-           (list :tag "Group"
-                 (cons
-                  (const :tag "Title" :title)
-                  (string :tag "Title"))
-                 (cons
-                  (const :tag "Sort function" :sort-fn)
-                  (choice
-                   function
-                   (const :tag "None" nil)))
-                 (cons
-                  (const :tag "Elements" :elements)
-                  elfeed-summary-group))
+           (cons :tag "Group"
+                 (const group)
+                 (list :tag "Group params"
+                       (cons
+                        (const :tag "Title" :title)
+                        (string :tag "Title"))
+                       (cons
+                        (const :tag "Sort function" :sort-fn)
+                        (choice
+                         function
+                         (const :tag "None" nil)))
+                       (cons
+                        (const :tag "Elements" :elements)
+                        elfeed-summary-group)))
            elfeed-summary-query)))
 
 (defgroup elfeed-summary ()
   "Feed summary inteface for elfeed."
   :group 'elfeed)
 
-(defcustom elfeed-summary-settings '(((:title . "All feeds")
-                                      (:sort-fn . string-lessp)
-                                      (:elements nil)))
-  "Elfeed summary buffer settings."
+(defcustom elfeed-summary-settings '((group (:title . "All feeds")
+                                            (:sort-fn . string-lessp)
+                                            (:elements :all)))
+  "Elfeed summary buffer settings.
+
+This is a list of these possible items:
+- group
+- query
+- a few special forms
+
+Groups are used to group queries under collapsible sections.
+
+A group is a cons cell like (group . <params>), where params are an
+alist with the following attributes:
+- `:title' (mandatory)
+- `:elements' (mandatory) - also a list of groups and queries
+- `:sort-fn' - function used to sort titles of feeds, found by queries
+  in `:elements'.  E.g. `string-greaterp' for alphabetical order.
+
+Query is a form that extract a subset of elfeed feeds based on
+some criteria.  In the summary buffer, each feed found by the
+query will be represented as a line.
+
+Query can be:
+- A symbol of a tag.
+  A feed will be matched if it has that tag.
+- `:all'.  Will match anything.
+- `(title . \"string\")' or `(title . <form>)'
+  Match feed title with `string-match-p'.  <form> makes sense if you
+  want to pass something like `rx'.
+- `(author . \"string\")' or `(author . <form>)'
+- `(url . \"string\")' or `(url . <form>)'
+- `(and <q-1> <q-2> ... <q-n>)'
+  Match if all the conditions 1, 2, ..., n match.
+- `(or <q-1> <q-2> ... <q-n>)' or `(<q-1> <q-2> ... <q-n>)'
+  Match if any of the conditions 1, 2, ..., n match.
+- `(not <query>)'
+
+Feed tags are taken from `elfeed-feeds'.
+
+Query examples:
+- `(emacs lisp)'
+  Return all feeds that have either \"emacs\" or \"lisp\" tags.
+- `(and emacs lisp)'
+  Return all feeds that have both \"emacs\" and \"lisp\" tags.
+- `(and (title . \"Emacs\") (not planets))
+  Return all feeds that have \"Emacs\" in their title and don't have
+  the \"planets\" tag.
+
+Available special forms:
+- `:misc' - print out feeds, not found by any query above.
+- `:unread' - a special feed of all unread entries."
   :group 'elfeed-summary
   :type 'elfeed-summary-group)
 
+(defcustom elfeed-summary-look-back (* 60 60 24 180)
+  "TODO"
+  :group 'elfeed-summary
+  :type 'integer)
+
+(defcustom elfeed-summary-unread-tag 'unread
+  "Unread tag"
+  :group 'elfeed-summary
+  :type 'symbol)
+
+(defface elfeed-summary-group-face
+  '((t (:inherit magit-section-heading)))
+  "Default face for the elfeed-summary group."
+  :group 'elfeed-summary)
+
 (cl-defun elfeed-summary--match-tag (query &key tags title url author title-meta)
   "Check if attributes of elfeed feed match QUERY.
 
-QUERY is a form as described in TODO.
+QUERY is a form as described in `elfeed-summary-settings'.
 
 TAGS is a list of tags from `elfeed-feeds', TITLE, URL, AUTHOR
 and TITLE-META are attributes of the `elfeed-db-feed'."
   (cond
+   ;; `:all'
+   ((equal query :all) t)
    ;; symbol
    ((symbolp query) (member query tags))
    ;; (title . "Title")
@@ -143,6 +214,16 @@ and TITLE-META are attributes of the `elfeed-db-feed'."
         :url url
         :author author))
      (cdr query)))
+   ;; (not <query>)
+   ((eq (car query) 'not)
+    (not
+     (elfeed-summary--match-tag
+      (cdr query)
+      :tags tags
+      :title title
+      :title-meta title-meta
+      :url url
+      :author author)))
    ;; (or <query-1> <query-2> ... <query-n>)
    ;; (<query-1> <query-2> ... <query-n>)
    (t (seq-some
@@ -161,7 +242,7 @@ and TITLE-META are attributes of the `elfeed-db-feed'."
 (defun elfeed-summary--get-feeds (query)
   "Get elfeed feeds that match QUERY.
 
-QUERY is described in TODO."
+QUERY is described in `elfeed-summary-settings'."
   (cl-loop for feed in elfeed-feeds
            for url = (car feed)
            for tags = (cdr feed)
@@ -175,5 +256,77 @@ QUERY is described in TODO."
                :author (plist-get (car (elfeed-feed-author feed)) :name))
            collect feed))
 
+(defun elfeed-summary--extract-feeds (params)
+  (cl-loop for param in params
+           if (and (listp param) (eq (car param) 'group))
+           append (elfeed-summary--extract-feeds
+                   (cdr (assoc :elements (cdr param))))
+           else append (elfeed-summary--get-feeds param)))
+
+(defun elfeed-summary--build-tree-feed (feed unread-count total-count)
+  (let* ((unread (or (gethash (elfeed-feed-id feed) unread-count) 0))
+         (tags (alist-get (elfeed-feed-id feed) elfeed-feeds
+                          nil nil #'equal))
+         (all-tags (if (< 0 unread)
+                       (cons elfeed-summary-unread-tag tags)
+                     tags)))
+    `((feed . ,feed)
+      (unread . ,unread)
+      (total . ,(or (gethash (elfeed-feed-id feed) total-count) 0))
+      (faces . ,(elfeed-search--faces all-tags))
+      (tags . ,all-tags))))
+
+(defun elfeed-summary--build-tree-unread (unread-count)
+  (let ((unread (apply #'+ (maphash (lambda (k v) v) unread-count))))
+    `((feed . ,(elfeed-feed--create
+                :id unread
+                :title "Unread"))
+      (unread . ,unread)
+      (total . ,unread))))
+
+(defun elfeed-summary--build-tree (params unread-count total-count misc-feeds)
+  (cl-loop for param in params
+           if (and (listp param) (eq (car param) 'group))
+           collect `(,param
+                     (children . ,(elfeed-summary--build-tree
+                                   (cdr (assoc :elements (cdr param)))
+                                   unread-count total-count misc-feeds)))
+           else if (eq param :misc)
+           append (cl-loop for feed in misc-feeds
+                           collect (elfeed-summary--build-tree-feed
+                                    feed unread-count total-count))
+           else if (eq param :unread)
+           collect (elfeed-summary--build-tree-unread unread-count)
+           else
+           append (cl-loop for feed in (elfeed-summary--get-feeds param)
+                           collect (elfeed-summary--build-tree-feed
+                                    feed unread-count total-count))))
+
+(defun elfeed-summary--get-data ()
+  (let* ((feeds (elfeed-summary--extract-feeds
+                 elfeed-summary-settings))
+         (all-feeds (mapcar #'car elfeed-feeds))
+         (misc-feeds
+          (thread-last feeds
+                       (mapcar #'elfeed-feed-id)
+                       (seq-difference all-feeds)
+                       (mapcar #'elfeed-db-get-feed)))
+         (unread-count (make-hash-table :test #'equal))
+         (total-count (make-hash-table :test #'equal)))
+    (with-elfeed-db-visit (entry feed)
+      (puthash (elfeed-feed-id feed)
+               (1+ (or (gethash (elfeed-feed-id feed) total-count) 0))
+               total-count)
+      (when (member elfeed-summary-unread-tag (elfeed-entry-tags entry))
+        (puthash (elfeed-feed-id feed)
+                 (1+ (or (gethash (elfeed-feed-id feed) unread-count) 0))
+                 unread-count))
+      (when (> (- (time-convert nil 'integer)
+                  elfeed-summary-look-back)
+               (elfeed-entry-date entry))
+        (elfeed-db-return)))
+    (elfeed-summary--build-tree elfeed-summary-settings
+                                unread-count total-count misc-feeds)))
+
 (provide 'elfeed-summary)
 ;;; elfeed-summary.el ends here