diff --git a/nest_frontend/components/interactive/BoxFilterContains.js b/nest_frontend/components/interactive/BoxFilterContains.js
index 4b57660..545d263 100644
--- a/nest_frontend/components/interactive/BoxFilterContains.js
+++ b/nest_frontend/components/interactive/BoxFilterContains.js
@@ -2,7 +2,7 @@ import React from "react"
 import BoxFull from "../base/BoxFull"
 import useRepositoryViewer from "../../hooks/useRepositoryViewer"
 import useStrings from "../../hooks/useStrings"
-import { ContainsFilter } from "../../utils/Filter"
+import { FilterContains } from "../../utils/Filter"
 import FormInlineText from "./FormInlineText"
 import { faFont } from "@fortawesome/free-solid-svg-icons"
 import { FontAwesomeIcon } from "@fortawesome/react-fontawesome"
@@ -13,7 +13,7 @@ export default function BoxFilterContains({ ...props }) {
     const { appendFilter } = useRepositoryViewer()
 
     const submit = value => {
-        appendFilter(new ContainsFilter(false, value))
+        appendFilter(new FilterContains(false, value))
     }
 
     // TODO: add this string
diff --git a/nest_frontend/components/interactive/BoxFilterDatetime.js b/nest_frontend/components/interactive/BoxFilterDatetime.js
index 8fde916..ab0c1ff 100644
--- a/nest_frontend/components/interactive/BoxFilterDatetime.js
+++ b/nest_frontend/components/interactive/BoxFilterDatetime.js
@@ -3,7 +3,7 @@ import BoxFull from "../base/BoxFull"
 import { faClock, faHashtag } from "@fortawesome/free-solid-svg-icons"
 import useRepositoryViewer from "../../hooks/useRepositoryViewer"
 import useStrings from "../../hooks/useStrings"
-import { AfterDatetimeFilter } from "../../utils/Filter"
+import { FilterInsideTimeRay } from "../../utils/Filter"
 import { FontAwesomeIcon } from "@fortawesome/react-fontawesome"
 import FormInlineBADatetime from "./FormInlineBADatetime"
 
@@ -13,7 +13,7 @@ export default function BoxFilterDatetime({ ...props }) {
     const { appendFilter } = useRepositoryViewer()
 
     const submit = ({ date, isBefore }) => {
-        appendFilter(new AfterDatetimeFilter(isBefore, date))
+        appendFilter(new FilterInsideTimeRay(isBefore, date))
     }
 
     return (
diff --git a/nest_frontend/components/interactive/BoxFilterHasPlace.js b/nest_frontend/components/interactive/BoxFilterHasPlace.js
index b317b18..ffaa711 100644
--- a/nest_frontend/components/interactive/BoxFilterHasPlace.js
+++ b/nest_frontend/components/interactive/BoxFilterHasPlace.js
@@ -5,7 +5,7 @@ import useRepositoryViewer from "../../hooks/useRepositoryViewer"
 import useStrings from "../../hooks/useStrings"
 import { FontAwesomeIcon } from "@fortawesome/react-fontawesome"
 import { faLocationArrow, faPlus } from "@fortawesome/free-solid-svg-icons"
-import { HasPlaceFilter } from "../../utils/Filter"
+import { FilterWithPlace } from "../../utils/Filter"
 import ButtonIconOnly from "../base/ButtonIconOnly"
 
 
@@ -15,7 +15,7 @@ export default function BoxFilterHasPlace({ ...props }) {
     const { appendFilter } = useRepositoryViewer()
 
     const submit = () => {
-        appendFilter(new HasPlaceFilter(false))
+        appendFilter(new FilterWithPlace(false))
     }
 
     // TODO: translate this
diff --git a/nest_frontend/components/interactive/BoxFilterHashtag.js b/nest_frontend/components/interactive/BoxFilterHashtag.js
index 76aba03..211d461 100644
--- a/nest_frontend/components/interactive/BoxFilterHashtag.js
+++ b/nest_frontend/components/interactive/BoxFilterHashtag.js
@@ -3,7 +3,7 @@ import BoxFull from "../base/BoxFull"
 import { faClock } from "@fortawesome/free-solid-svg-icons"
 import useRepositoryViewer from "../../hooks/useRepositoryViewer"
 import useStrings from "../../hooks/useStrings"
-import { HashtagFilter } from "../../utils/Filter"
+import { FilterHashtag } from "../../utils/Filter"
 import FormInlineHashtag from "./FormInlineHashtag"
 import { FontAwesomeIcon } from "@fortawesome/react-fontawesome"
 
@@ -13,7 +13,7 @@ export default function BoxFilterHashtag({ ...props }) {
     const { appendFilter } = useRepositoryViewer()
 
     const submit = value => {
-        appendFilter(new HashtagFilter(false, value))
+        appendFilter(new FilterHashtag(false, value))
     }
 
     return (
diff --git a/nest_frontend/components/interactive/BoxFilterLocation.js b/nest_frontend/components/interactive/BoxFilterLocation.js
index 851dc49..5c036f7 100644
--- a/nest_frontend/components/interactive/BoxFilterLocation.js
+++ b/nest_frontend/components/interactive/BoxFilterLocation.js
@@ -6,7 +6,7 @@ import useStrings from "../../hooks/useStrings"
 import { FontAwesomeIcon } from "@fortawesome/react-fontawesome"
 import { faMapPin } from "@fortawesome/free-solid-svg-icons"
 import FormInlineLocation from "./FormInlineLocation"
-import { LocationRadiusFilter } from "../../utils/Filter"
+import { FilterInsideMapArea } from "../../utils/Filter"
 
 
 export default function BoxFilterLocation({ ...props }) {
@@ -15,7 +15,7 @@ export default function BoxFilterLocation({ ...props }) {
     const { appendFilter, mapViewHook } = useRepositoryViewer()
 
     const submit = () => {
-        appendFilter(new LocationRadiusFilter(false, mapViewHook.center, mapViewHook.radius))
+        appendFilter(new FilterInsideMapArea(false, mapViewHook.center, mapViewHook.radius))
     }
 
     return (
diff --git a/nest_frontend/components/interactive/BoxFilterUser.js b/nest_frontend/components/interactive/BoxFilterUser.js
index 9efd651..edcb702 100644
--- a/nest_frontend/components/interactive/BoxFilterUser.js
+++ b/nest_frontend/components/interactive/BoxFilterUser.js
@@ -3,7 +3,7 @@ import BoxFull from "../base/BoxFull"
 import { faAt } from "@fortawesome/free-solid-svg-icons"
 import useRepositoryViewer from "../../hooks/useRepositoryViewer"
 import useStrings from "../../hooks/useStrings"
-import { UserFilter } from "../../utils/Filter"
+import { FilterPoster } from "../../utils/Filter"
 import FormInlineUser from "./FormInlineUser"
 import { FontAwesomeIcon } from "@fortawesome/react-fontawesome"
 
@@ -16,7 +16,7 @@ export default function BoxFilterUser({ ...props }) {
     const { appendFilter } = useRepositoryViewer()
 
     const submit = value => {
-        appendFilter(new UserFilter(false, value))
+        appendFilter(new FilterPoster(false, value))
     }
 
     return (
diff --git a/nest_frontend/components/interactive/BoxVisualizationWordcloud.js b/nest_frontend/components/interactive/BoxVisualizationWordcloud.js
index 9072146..be53923 100644
--- a/nest_frontend/components/interactive/BoxVisualizationWordcloud.js
+++ b/nest_frontend/components/interactive/BoxVisualizationWordcloud.js
@@ -4,7 +4,7 @@ import ContextLanguage from "../../contexts/ContextLanguage"
 import BoxFull from "../base/BoxFull"
 import Empty from "./Empty"
 import ContextRepositoryViewer from "../../contexts/ContextRepositoryViewer"
-import { ContainsFilter } from "../../utils/Filter"
+import { FilterContains } from "../../utils/Filter"
 
 
 export default function BoxVisualizationWordcloud({ ...props }) {
@@ -20,7 +20,7 @@ export default function BoxVisualizationWordcloud({ ...props }) {
     }
 
     const onWordClick = word => {
-        appendFilter(new ContainsFilter(false, word.text))
+        appendFilter(new FilterContains(false, word.text))
     }
 
     return (
diff --git a/nest_frontend/objects/Filter.js b/nest_frontend/objects/Filter.js
new file mode 100644
index 0000000..c8f8892
--- /dev/null
+++ b/nest_frontend/objects/Filter.js
@@ -0,0 +1,222 @@
+import {
+    faAt,
+    faClock,
+    faFilter,
+    faFont,
+    faHashtag,
+    faLocationArrow,
+    faMapMarkerAlt,
+    faMapPin,
+} from "@fortawesome/free-solid-svg-icons"
+
+
+/**
+ * A filter applicable in the Analysis mode.
+ */
+export class Filter {
+    negate
+
+    /**
+     * @param negate - If the filter output should be reversed.
+     */
+    constructor(negate = false) {
+        this.negate = negate
+    }
+
+    /**
+     * Check if a tweet passed through the filter or not, without applying `negate`.
+     *
+     * @param tweet - The tweet to check.
+     * @returns {boolean}
+     */
+    check(tweet) {
+        return true
+    }
+
+    /**
+     * Check if a tweet passed through the filter or not, applying `negate`.
+     *
+     * @param tweet - The tweet to check.
+     * @returns {boolean}
+     */
+    exec(tweet) {
+        return Boolean(this.check(tweet) ^ this.negate)
+    }
+
+    display() {
+        return {
+            color: "Grey",
+            icon: faFilter,
+            children: this.negate ? "False" : "True"
+        }
+    }
+}
+
+
+/**
+ * Checks if a tweet contains a string.
+ */
+export class FilterContains extends Filter {
+    string
+
+    constructor(word, negate = false) {
+        super(negate)
+        this.string = word.toLowerCase().trim()
+    }
+
+    check(tweet) {
+        return tweet.content?.toLowerCase().includes(this.string)
+    }
+
+    display() {
+        return {
+            color: "Grey",
+            icon: faFont,
+            children: this.string
+        }
+    }
+}
+
+
+/**
+ * Check if a tweet contains an hashtag.
+ */
+export class FilterHashtag extends FilterContains {
+    hashtag
+
+    constructor(hashtag, negate = false) {
+        super(negate, `#${hashtag}`)
+        this.hashtag = hashtag
+    }
+
+    display() {
+        return {
+            color: "Grey",
+            icon: faHashtag,
+            children: this.hashtag
+        }
+    }
+}
+
+
+/**
+ * Check if a tweet was posted by a certain user.
+ */
+export class FilterPoster extends Filter {
+    poster
+
+    constructor(poster, negate = false) {
+        super(negate)
+        this.poster = poster
+    }
+
+    check(tweet) {
+        return tweet.poster.toLowerCase() === this.poster.toLowerCase()
+    }
+
+    display() {
+        return {
+            color: "Green",
+            icon: faAt,
+            children: this.poster
+        }
+    }
+}
+
+
+/**
+ * Check if a tweet contains `location` metadata.
+ */
+export class FilterWithLocation extends Filter {
+    constructor(negate = false) {
+        super(negate)
+    }
+
+    check(tweet) {
+        return Boolean(tweet["location"])
+    }
+
+    display() {
+        return {
+            color: "Red",
+            icon: faLocationArrow,
+            children: ""
+        }
+    }
+}
+
+
+/**
+ * Check if a tweet contains `place` metadata.
+ */
+export class FilterWithPlace extends Filter {
+    constructor(negate = false) {
+        super(negate)
+    }
+
+    check(tweet) {
+        return Boolean(tweet["place"])
+    }
+
+    display() {
+        return {
+            color: "Red",
+            icon: faMapMarkerAlt,
+            children: ""
+        }
+    }
+}
+
+
+/**
+ * Check if a tweet's `location` is inside a {@link MapArea}.
+ */
+export class FilterInsideMapArea extends FilterWithLocation {
+    mapArea
+
+    constructor(mapArea, negate = false) {
+        super(negate)
+        this.mapArea = mapArea
+    }
+
+    check(tweet) {
+        if(!super.check(tweet)) {
+            return false
+        }
+
+        return this.mapArea.includes(tweet.location)
+    }
+
+    display() {
+        return {
+            color: "Red",
+            icon: faLocationArrow,
+            children: this.mapArea.toHumanString()
+        }
+    }
+}
+
+
+/**
+ * Check if a tweet's `post_time` is inside a {@link TimeRay}.
+ */
+export class FilterInsideTimeRay extends Filter {
+    timeRay
+
+    constructor(timeRay, negate = false) {
+        super(negate)
+        this.timeRay = timeRay
+    }
+
+    check(tweet) {
+        return this.datetime < new Date(tweet["insert_time"])
+    }
+
+    display() {
+        return {
+            color: "Yellow",
+            icon: faClock,
+            children: this.timeRay.toString()
+        }
+    }
+}
diff --git a/nest_frontend/objects/MapArea.js b/nest_frontend/objects/MapArea.js
index a222742..f1f21ac 100644
--- a/nest_frontend/objects/MapArea.js
+++ b/nest_frontend/objects/MapArea.js
@@ -36,7 +36,7 @@ export default class MapArea {
      * @returns {string}
      */
     toString() {
-        return `${this.radius} ${this.center.toString()}`
+        return `< ${this.radius} ${this.center.toString()}`
     }
 
     /**
@@ -47,9 +47,9 @@ export default class MapArea {
     toHumanString() {
         if(this.radius >= 2000) {
             const kmRadius = Math.round(this.radius / 1000)
-            return `${kmRadius}km ${this.center.toHumanString()}`
+            return `< ${kmRadius}km ${this.center.toHumanString()}`
         }
-        return `${this.radius}m ${this.center.toHumanString()}`
+        return `< ${this.radius}m ${this.center.toHumanString()}`
     }
 
     /**
diff --git a/nest_frontend/objects/MapArea.test.js b/nest_frontend/objects/MapArea.test.js
index 409f015..cf64005 100644
--- a/nest_frontend/objects/MapArea.test.js
+++ b/nest_frontend/objects/MapArea.test.js
@@ -9,5 +9,5 @@ test("MapArea can be constructed", () => {
 
 test("MapArea can be rendered to a spec-compatible string", () => {
     const mapArea = new MapArea(1000, new Coordinates(0.0, 0.0))
-    expect(mapArea.toString()).toBe("1000 0.0000000 0.0000000")
+    expect(mapArea.toString()).toBe("< 1000 0.0000000 0.0000000")
 })
diff --git a/nest_frontend/objects/TimeRay.js b/nest_frontend/objects/TimeRay.js
index 04bde14..fcd2184 100644
--- a/nest_frontend/objects/TimeRay.js
+++ b/nest_frontend/objects/TimeRay.js
@@ -21,4 +21,8 @@ export default class TimeRay {
     toString() {
         return `${this.isBefore ? "<" : ">"} ${this.date.toISOString()}`
     }
+
+    includes(date) {
+        return Boolean((this.date > date) ^ this.isBefore)
+    }
 }
diff --git a/nest_frontend/utils/Filter.js b/nest_frontend/utils/Filter.js
deleted file mode 100644
index 0f6b737..0000000
--- a/nest_frontend/utils/Filter.js
+++ /dev/null
@@ -1,221 +0,0 @@
-import { Location } from "./location"
-import {
-    faAt,
-    faClock,
-    faFilter,
-    faFont,
-    faHashtag,
-    faLocationArrow,
-    faMapMarkerAlt,
-    faMapPin,
-} from "@fortawesome/free-solid-svg-icons"
-
-
-export class Filter {
-    negate
-
-    constructor(negate) {
-        this.negate = negate
-    }
-
-    check(tweet) {
-        return true
-    }
-
-    exec(tweet) {
-        return this.check(tweet) ^ this.negate
-    }
-
-    color() {
-        return "Grey"
-    }
-
-    icon() {
-        return faFilter
-    }
-
-    text() {
-        return this.negate ? "False" : "True"
-    }
-}
-
-
-export class ContainsFilter extends Filter {
-    word
-
-    constructor(negate, word) {
-        super(negate)
-        this.word = word.toLowerCase().trim()
-    }
-
-    check(tweet) {
-        return tweet.content?.toLowerCase().includes(this.word)
-    }
-
-    color() {
-        return "Grey"
-    }
-
-    icon() {
-        return faFont
-    }
-
-    text() {
-        return this.word
-    }
-}
-
-
-export class HashtagFilter extends ContainsFilter {
-    hashtag
-
-    constructor(negate, hashtag) {
-        super(negate, `#${hashtag}`)
-        this.hashtag = hashtag
-    }
-
-    icon() {
-        return faHashtag
-    }
-
-    text() {
-        return this.hashtag
-    }
-}
-
-
-export class UserFilter extends Filter {
-    user
-
-    constructor(negate, user) {
-        super(negate)
-        this.user = user.toLowerCase().trim().replace(/^@/, "")
-    }
-
-    check(tweet) {
-        return tweet.poster.toLowerCase() === this.user
-    }
-
-    color() {
-        return "Green"
-    }
-
-    icon() {
-        return faAt
-    }
-
-    text() {
-        return this.user
-    }
-}
-
-
-export class HasLocationFilter extends Filter {
-    constructor(negate) {
-        super(negate)
-    }
-
-    check(tweet) {
-        return Boolean(tweet["location"])
-    }
-
-    color() {
-        return "Red"
-    }
-
-    icon() {
-        return faMapMarkerAlt
-    }
-
-    text() {
-        return ""
-    }
-}
-
-
-export class HasPlaceFilter extends Filter {
-    constructor(negate) {
-        super(negate)
-    }
-
-    check(tweet) {
-        return Boolean(tweet["place"])
-    }
-
-    color() {
-        return "Red"
-    }
-
-    icon() {
-        return faLocationArrow
-    }
-
-    text() {
-        return ""
-    }
-}
-
-
-export class LocationRadiusFilter extends HasLocationFilter {
-    center
-    radius
-
-    constructor(negate, center, radius) {
-        super(negate)
-        this.center = center
-        this.radius = radius
-    }
-
-    check(tweet) {
-        if(!super.check(tweet)) {
-            return false
-        }
-
-        // FIXME: Maths is hard
-        const location = Location.fromTweet(tweet)
-        const latDiff = Math.abs(location.lat - this.center.lat)
-        const lngDiff = Math.abs(location.lng - this.center.lng)
-        const squaredDistance = Math.pow(latDiff, 2) + Math.pow(lngDiff, 2)
-        const squaredRadius = Math.pow(this.radius, 2)
-
-        return squaredDistance < squaredRadius
-    }
-
-    color() {
-        return "Red"
-    }
-
-    icon() {
-        return faMapPin
-    }
-
-    text() {
-        return `< ${this.radius}m ${this.center.lat.toFixed(3)} ${this.center.lng.toFixed(3)}`
-    }
-}
-
-
-export class AfterDatetimeFilter extends Filter {
-    datetime
-
-    constructor(negate, datetime) {
-        super(negate)
-        this.datetime = datetime
-    }
-
-    check(tweet) {
-        return this.datetime < new Date(tweet["insert_time"])
-    }
-
-    color() {
-        return "Yellow"
-    }
-
-    icon() {
-        return faClock
-    }
-
-    text() {
-        return `${this.negate ? "<" : ">"} ${this.datetime.toISOString()}`
-    }
-}
\ No newline at end of file