diff --git a/.changeset/calm-types-erase.md b/.changeset/calm-types-erase.md
new file mode 100644
index 00000000..dd377244
--- /dev/null
+++ b/.changeset/calm-types-erase.md
@@ -0,0 +1,5 @@
+---
+'@remote-dom/polyfill': patch
+---
+
+Make the Polyfill source compatible with type stripping by replacing TypeScript enums and a parameter property with erasable syntax.
diff --git a/packages/polyfill/source/Attr.ts b/packages/polyfill/source/Attr.ts
index a43d3660..650f0c93 100644
--- a/packages/polyfill/source/Attr.ts
+++ b/packages/polyfill/source/Attr.ts
@@ -4,15 +4,16 @@ import {
   VALUE,
   OWNER_ELEMENT,
   NAME,
-  NamespaceURI,
-  NodeType,
+  NODE_TYPE_ATTRIBUTE,
+  type NamespaceURI,
+  type NodeType,
   HOOKS,
 } from './constants.ts';
 import {Node} from './Node.ts';
 import type {Element} from './Element.ts';
 
 export class Attr extends Node {
-  nodeType = NodeType.ATTRIBUTE_NODE;
+  nodeType: NodeType = NODE_TYPE_ATTRIBUTE;
   [NS]: NamespaceURI | null = null;
   [NEXT]: Attr | null = null;
   [VALUE]: string;
diff --git a/packages/polyfill/source/Comment.ts b/packages/polyfill/source/Comment.ts
index c3ca61b7..80d50109 100644
--- a/packages/polyfill/source/Comment.ts
+++ b/packages/polyfill/source/Comment.ts
@@ -1,7 +1,7 @@
-import {NAME} from './constants.ts';
+import {NAME, NODE_TYPE_COMMENT, type NodeType} from './constants.ts';
 import {CharacterData} from './CharacterData.ts';
 
 export class Comment extends CharacterData {
-  nodeType = 8;
+  nodeType: NodeType = NODE_TYPE_COMMENT;
   [NAME] = '#comment';
 }
diff --git a/packages/polyfill/source/Document.ts b/packages/polyfill/source/Document.ts
index 625cde69..cabe2332 100644
--- a/packages/polyfill/source/Document.ts
+++ b/packages/polyfill/source/Document.ts
@@ -1,8 +1,10 @@
 import {
   NS,
   NAME,
-  NamespaceURI,
-  NodeType,
+  NODE_TYPE_DOCUMENT,
+  SVG_NAMESPACE,
+  type NamespaceURI,
+  type NodeType,
   OWNER_DOCUMENT,
   HOOKS,
   IS_CONNECTED,
@@ -28,7 +30,7 @@ import {HTMLHeadElement} from './HTMLHeadElement.ts';
 import {HTMLHtmlElement} from './HTMLHtmlElement.ts';
 
 export class Document extends ParentNode {
-  nodeType = NodeType.DOCUMENT_NODE;
+  nodeType: NodeType = NODE_TYPE_DOCUMENT;
   [NAME] = '#document';
   body: HTMLBodyElement;
   head: HTMLHeadElement;
@@ -115,7 +117,7 @@ export function createElement<T extends Element>(
   let element: T;
   const lowerName = String(name).toLowerCase();
 
-  if (namespace === NamespaceURI.SVG) {
+  if (namespace === SVG_NAMESPACE) {
     element = new SVGElement() as any;
   } else if (lowerName === 'template') {
     element = new HTMLTemplateElement() as any;
diff --git a/packages/polyfill/source/DocumentFragment.ts b/packages/polyfill/source/DocumentFragment.ts
index 0853da10..f9d2c25e 100644
--- a/packages/polyfill/source/DocumentFragment.ts
+++ b/packages/polyfill/source/DocumentFragment.ts
@@ -1,9 +1,14 @@
-import {NAME, OWNER_DOCUMENT, NodeType} from './constants.ts';
+import {
+  NAME,
+  OWNER_DOCUMENT,
+  NODE_TYPE_DOCUMENT_FRAGMENT,
+  type NodeType,
+} from './constants.ts';
 import {ParentNode} from './ParentNode.ts';
 import {getElementById as findElementById} from './shared.ts';
 
 export class DocumentFragment extends ParentNode {
-  nodeType = NodeType.DOCUMENT_FRAGMENT_NODE;
+  nodeType: NodeType = NODE_TYPE_DOCUMENT_FRAGMENT;
   [NAME] = '#document-fragment';
   [OWNER_DOCUMENT] = (typeof window !== 'undefined'
     ? window.document
diff --git a/packages/polyfill/source/Element.ts b/packages/polyfill/source/Element.ts
index 8f6e3837..d4537cab 100644
--- a/packages/polyfill/source/Element.ts
+++ b/packages/polyfill/source/Element.ts
@@ -1,4 +1,11 @@
-import {NS, ATTRIBUTES, NamespaceURI, NodeType} from './constants.ts';
+import {
+  NS,
+  ATTRIBUTES,
+  HTML_NAMESPACE,
+  NODE_TYPE_ELEMENT,
+  type NamespaceURI,
+  type NodeType,
+} from './constants.ts';
 import {ParentNode} from './ParentNode.ts';
 import {NamedNodeMap} from './NamedNodeMap.ts';
 import {Attr} from './Attr.ts';
@@ -8,9 +15,9 @@ import {getElementsByTagName as findElementsByTagName} from './shared.ts';
 export class Element extends ParentNode {
   static readonly observedAttributes?: string[];
 
-  nodeType = NodeType.ELEMENT_NODE;
+  nodeType: NodeType = NODE_TYPE_ELEMENT;
 
-  [NS] = NamespaceURI.XHTML;
+  [NS]: NamespaceURI = HTML_NAMESPACE;
   get namespaceURI() {
     return this[NS];
   }
diff --git a/packages/polyfill/source/Event.ts b/packages/polyfill/source/Event.ts
index e5793dc1..a2d2db75 100644
--- a/packages/polyfill/source/Event.ts
+++ b/packages/polyfill/source/Event.ts
@@ -6,14 +6,12 @@ import {
 } from './constants.ts';
 import type {EventTarget} from './EventTarget.ts';
 
-// TODO: Replace this enum with one-way constants, matching the DOM and Web IDL.
-// @ts-expect-error -- Legacy enum; keep this exception scoped to this declaration.
-export const enum EventPhase {
-  NONE = 0,
-  CAPTURING_PHASE = 1,
-  AT_TARGET = 2,
-  BUBBLING_PHASE = 3,
-}
+export const EVENT_PHASE_NONE = 0;
+export const EVENT_PHASE_CAPTURING = 1;
+export const EVENT_PHASE_AT_TARGET = 2;
+export const EVENT_PHASE_BUBBLING = 3;
+
+export type EventPhase = number;
 
 export const CAPTURE_MARKER = '@';
 
@@ -29,16 +27,17 @@ const now =
     : performance.now.bind(performance);
 
 export class Event {
-  static NONE = EventPhase.NONE;
-  static CAPTURING_PHASE = EventPhase.CAPTURING_PHASE;
-  static AT_TARGET = EventPhase.AT_TARGET;
-  static BUBBLING_PHASE = EventPhase.BUBBLING_PHASE;
+  static NONE: EventPhase = EVENT_PHASE_NONE;
+  static CAPTURING_PHASE: EventPhase = EVENT_PHASE_CAPTURING;
+  static AT_TARGET: EventPhase = EVENT_PHASE_AT_TARGET;
+  static BUBBLING_PHASE: EventPhase = EVENT_PHASE_BUBBLING;
 
-  // NONE = EventPhase.NONE;
-  // CAPTURING_PHASE = EventPhase.CAPTURING_PHASE;
-  // AT_TARGET = EventPhase.AT_TARGET;
-  // BUBBLING_PHASE = EventPhase.BUBBLING_PHASE;
+  // NONE = EVENT_PHASE_NONE;
+  // CAPTURING_PHASE = EVENT_PHASE_CAPTURING;
+  // AT_TARGET = EVENT_PHASE_AT_TARGET;
+  // BUBBLING_PHASE = EVENT_PHASE_BUBBLING;
 
+  type: string;
   timeStamp = now();
   target: EventTarget | null = null;
   currentTarget: EventTarget | null = null;
@@ -48,18 +47,15 @@ export class Event {
   composed = false;
   defaultPrevented = false;
   cancelBubble = false;
-  eventPhase: EventPhase = 0;
+  eventPhase: EventPhase = EVENT_PHASE_NONE;
   // private inPassiveListener = false;
   data?: any;
   [PATH]: EventTarget[] = [];
   [IS_TRUSTED]!: boolean;
   [STOP_IMMEDIATE_PROPAGATION] = false;
 
-  constructor(
-    // @ts-expect-error -- Legacy parameter property; keep this exception scoped to this declaration.
-    public type: string,
-    options?: EventInit,
-  ) {
+  constructor(type: string, options?: EventInit) {
+    this.type = type;
     Object.defineProperty(this, IS_TRUSTED, {writable: true, value: false});
     if (options) {
       if (options.bubbles) this.bubbles = options.bubbles;
@@ -108,20 +104,18 @@ export class Event {
 export function fireEvent(
   event: Event,
   currentTarget: EventTarget,
-  phase: EventPhase.BUBBLING_PHASE | EventPhase.CAPTURING_PHASE,
+  phase: typeof EVENT_PHASE_BUBBLING | typeof EVENT_PHASE_CAPTURING,
 ): void {
   const listeners = currentTarget[LISTENERS];
   const list = listeners?.get(
-    `${event.type}${
-      phase === EventPhase.CAPTURING_PHASE ? CAPTURE_MARKER : ''
-    }`,
+    `${event.type}${phase === EVENT_PHASE_CAPTURING ? CAPTURE_MARKER : ''}`,
   );
 
   if (!list) return;
 
   for (const listener of list) {
     event.eventPhase =
-      event.target === currentTarget ? EventPhase.AT_TARGET : phase;
+      event.target === currentTarget ? EVENT_PHASE_AT_TARGET : phase;
     event.currentTarget = currentTarget;
 
     try {
diff --git a/packages/polyfill/source/EventTarget.ts b/packages/polyfill/source/EventTarget.ts
index ea448660..992ccb14 100644
--- a/packages/polyfill/source/EventTarget.ts
+++ b/packages/polyfill/source/EventTarget.ts
@@ -1,5 +1,9 @@
 import {HOOKS, PATH, LISTENERS, OWNER_DOCUMENT} from './constants.ts';
-import {fireEvent, EventPhase} from './Event.ts';
+import {
+  EVENT_PHASE_BUBBLING,
+  EVENT_PHASE_CAPTURING,
+  fireEvent,
+} from './Event.ts';
 import {CAPTURE_MARKER, type Event} from './Event.ts';
 import type {ChildNode} from './ChildNode.ts';
 import type {Document} from './Document.ts';
@@ -114,14 +118,14 @@ export class EventTarget {
     event[PATH] = path;
 
     for (let i = path.length; i--; ) {
-      fireEvent(event, path[i]!, EventPhase.CAPTURING_PHASE);
+      fireEvent(event, path[i]!, EVENT_PHASE_CAPTURING);
       if (event.cancelBubble) return event.defaultPrevented;
     }
 
     const bubblePath = event.bubbles ? path : path.slice(0, 1);
 
     for (let i = 0; i < bubblePath.length; i++) {
-      fireEvent(event, bubblePath[i]!, EventPhase.BUBBLING_PHASE);
+      fireEvent(event, bubblePath[i]!, EVENT_PHASE_BUBBLING);
       if (event.cancelBubble) return event.defaultPrevented;
     }
 
diff --git a/packages/polyfill/source/NamedNodeMap.ts b/packages/polyfill/source/NamedNodeMap.ts
index d82eac9f..d039cf79 100644
--- a/packages/polyfill/source/NamedNodeMap.ts
+++ b/packages/polyfill/source/NamedNodeMap.ts
@@ -3,7 +3,7 @@ import {
   OWNER_ELEMENT,
   NS,
   NEXT,
-  NamespaceURI,
+  type NamespaceURI,
   HOOKS,
 } from './constants.ts';
 import type {Attr} from './Attr.ts';
diff --git a/packages/polyfill/source/Node.ts b/packages/polyfill/source/Node.ts
index af1a5705..4c2c1ce2 100644
--- a/packages/polyfill/source/Node.ts
+++ b/packages/polyfill/source/Node.ts
@@ -5,8 +5,9 @@ import {
   CHILD,
   PREV,
   NEXT,
-  NamespaceURI,
-  NodeType,
+  HTML_NAMESPACE,
+  NODE_TYPE_NODE,
+  type NodeType,
   HOOKS,
   IS_CONNECTED,
 } from './constants.ts';
@@ -22,7 +23,7 @@ import {
 } from './shared.ts';
 
 export class Node extends EventTarget {
-  nodeType = NodeType.NODE;
+  nodeType: NodeType = NODE_TYPE_NODE;
 
   [OWNER_DOCUMENT]!: Document;
   [NAME] = '';
@@ -52,8 +53,8 @@ export class Node extends EventTarget {
     return this[IS_CONNECTED];
   }
 
-  isDefaultNamespace(namespace: string) {
-    return namespace === NamespaceURI.XHTML;
+  isDefaultNamespace(namespace: string): namespace is typeof HTML_NAMESPACE {
+    return namespace === HTML_NAMESPACE;
   }
 
   get parentNode() {
diff --git a/packages/polyfill/source/ParentNode.ts b/packages/polyfill/source/ParentNode.ts
index 7ed9bd81..e16c1967 100644
--- a/packages/polyfill/source/ParentNode.ts
+++ b/packages/polyfill/source/ParentNode.ts
@@ -4,7 +4,8 @@ import {
   PREV,
   PARENT,
   OWNER_DOCUMENT,
-  NodeType,
+  NODE_TYPE_DOCUMENT_FRAGMENT,
+  NODE_TYPE_ELEMENT,
   HOOKS,
   IS_CONNECTED,
 } from './constants.ts';
@@ -81,7 +82,7 @@ export class ParentNode extends ChildNode {
       }
     }
 
-    if (this.nodeType === NodeType.ELEMENT_NODE) {
+    if (this.nodeType === NODE_TYPE_ELEMENT) {
       this[HOOKS].removeChild?.(this as any, child as any, childNodesIndex);
     }
   }
@@ -105,7 +106,7 @@ export class ParentNode extends ChildNode {
 
   private insertInto(child: Node, before: Node | null) {
     // append the children of a DocumentFragment:
-    if (child.nodeType === NodeType.DOCUMENT_FRAGMENT_NODE) {
+    if (child.nodeType === NODE_TYPE_DOCUMENT_FRAGMENT) {
       let node = child[CHILD];
       while (node) {
         const next = node[NEXT];
@@ -144,7 +145,7 @@ export class ParentNode extends ChildNode {
     }
 
     const ownerDocument = this[OWNER_DOCUMENT];
-    const isElement = child.nodeType === NodeType.ELEMENT_NODE;
+    const isElement = child.nodeType === NODE_TYPE_ELEMENT;
 
     child[PARENT] = this;
     child[OWNER_DOCUMENT] = ownerDocument;
@@ -179,7 +180,7 @@ export class ParentNode extends ChildNode {
       }
     }
 
-    if (this.nodeType === NodeType.ELEMENT_NODE) {
+    if (this.nodeType === NODE_TYPE_ELEMENT) {
       this[HOOKS].insertChild?.(this as any, child as any, insertIndex);
     }
   }
diff --git a/packages/polyfill/source/SVGElement.ts b/packages/polyfill/source/SVGElement.ts
index 328b17f4..0ed95c52 100644
--- a/packages/polyfill/source/SVGElement.ts
+++ b/packages/polyfill/source/SVGElement.ts
@@ -1,8 +1,8 @@
-import {NS, NamespaceURI} from './constants.ts';
+import {NS, SVG_NAMESPACE, type NamespaceURI} from './constants.ts';
 import {Element} from './Element.ts';
 
 export class SVGElement extends Element {
-  [NS] = NamespaceURI.SVG;
+  [NS]: NamespaceURI = SVG_NAMESPACE;
 
   get ownerSVGElement() {
     let root: SVGElement | null = null;
diff --git a/packages/polyfill/source/Text.ts b/packages/polyfill/source/Text.ts
index fd64724d..47b39bd4 100644
--- a/packages/polyfill/source/Text.ts
+++ b/packages/polyfill/source/Text.ts
@@ -1,7 +1,7 @@
-import {NAME, NodeType} from './constants.ts';
+import {NAME, NODE_TYPE_TEXT, type NodeType} from './constants.ts';
 import {CharacterData} from './CharacterData.ts';
 
 export class Text extends CharacterData {
-  nodeType = NodeType.TEXT_NODE;
+  nodeType: NodeType = NODE_TYPE_TEXT;
   [NAME] = '#text';
 }
diff --git a/packages/polyfill/source/constants.ts b/packages/polyfill/source/constants.ts
index f304bea9..8175a8df 100644
--- a/packages/polyfill/source/constants.ts
+++ b/packages/polyfill/source/constants.ts
@@ -18,26 +18,22 @@ export const CONTENT = Symbol('content');
 export const HOOKS = Symbol('hooks');
 export const IS_CONNECTED = Symbol('is_connected');
 
-// TODO: Replace this enum with one-way constants, matching the DOM and Web IDL.
-// @ts-expect-error -- Legacy enum; keep this exception scoped to this declaration.
-export const enum NodeType {
-  NODE = 0,
-  ELEMENT_NODE = 1,
-  ATTRIBUTE_NODE = 2,
-  TEXT_NODE = 3,
-  CDATA_SECTION_NODE = 4,
-  ENTITY_REFERENCE_NODE = 5,
-  ENTITY_NODE = 6,
-  PROCESSING_INSTRUCTION_NODE = 7,
-  COMMENT_NODE = 8,
-  DOCUMENT_NODE = 9,
-  DOCUMENT_TYPE_NODE = 10,
-  DOCUMENT_FRAGMENT_NODE = 11,
-}
+export const NODE_TYPE_NODE = 0;
+export const NODE_TYPE_ELEMENT = 1;
+export const NODE_TYPE_ATTRIBUTE = 2;
+export const NODE_TYPE_TEXT = 3;
+export const NODE_TYPE_CDATA_SECTION = 4;
+export const NODE_TYPE_ENTITY_REFERENCE = 5;
+export const NODE_TYPE_ENTITY = 6;
+export const NODE_TYPE_PROCESSING_INSTRUCTION = 7;
+export const NODE_TYPE_COMMENT = 8;
+export const NODE_TYPE_DOCUMENT = 9;
+export const NODE_TYPE_DOCUMENT_TYPE = 10;
+export const NODE_TYPE_DOCUMENT_FRAGMENT = 11;
 
-// TODO: Replace this enum with namespace string constants, matching the DOM.
-// @ts-expect-error -- Legacy enum; keep this exception scoped to this declaration.
-export const enum NamespaceURI {
-  XHTML = 'http://www.w3.org/1999/xhtml',
-  SVG = 'http://www.w3.org/2000/svg',
-}
+export type NodeType = number;
+
+export const HTML_NAMESPACE = 'http://www.w3.org/1999/xhtml';
+export const SVG_NAMESPACE = 'http://www.w3.org/2000/svg';
+
+export type NamespaceURI = typeof HTML_NAMESPACE | typeof SVG_NAMESPACE;
diff --git a/packages/polyfill/source/selectors.ts b/packages/polyfill/source/selectors.ts
index 3d357247..be1d6d2c 100644
--- a/packages/polyfill/source/selectors.ts
+++ b/packages/polyfill/source/selectors.ts
@@ -1,31 +1,39 @@
-import {CHILD, NEXT, PARENT, PREV, NamespaceURI} from './constants.ts';
+import {CHILD, NEXT, PARENT, PREV, HTML_NAMESPACE} from './constants.ts';
 import {isElementNode} from './shared.ts';
 
 import type {Node} from './Node.ts';
 import type {Element} from './Element.ts';
 import type {ParentNode} from './ParentNode.ts';
 
-// TODO: Replace this enum with an erasable constant object.
-// @ts-expect-error -- Legacy enum; keep this exception scoped to this declaration.
-export const enum Combinator {
-  Descendant,
-  Child,
-  Sibling,
-  Adjacent,
-  Inner,
-}
+export const COMBINATOR_DESCENDANT = 0;
+export const COMBINATOR_CHILD = 1;
+export const COMBINATOR_SIBLING = 2;
+export const COMBINATOR_ADJACENT = 3;
+export const COMBINATOR_INNER = 4;
 
-// TODO: Replace this enum with an erasable constant object.
-// @ts-expect-error -- Legacy enum; keep this exception scoped to this declaration.
-export const enum MatcherType {
-  Unknown,
-  Element,
-  Id,
-  Class,
-  Attribute,
-  Pseudo,
-  Function,
-}
+export type Combinator =
+  | typeof COMBINATOR_DESCENDANT
+  | typeof COMBINATOR_CHILD
+  | typeof COMBINATOR_SIBLING
+  | typeof COMBINATOR_ADJACENT
+  | typeof COMBINATOR_INNER;
+
+export const MATCHER_UNKNOWN = 0;
+export const MATCHER_ELEMENT = 1;
+export const MATCHER_ID = 2;
+export const MATCHER_CLASS = 3;
+export const MATCHER_ATTRIBUTE = 4;
+export const MATCHER_PSEUDO = 5;
+export const MATCHER_FUNCTION = 6;
+
+export type MatcherType =
+  | typeof MATCHER_UNKNOWN
+  | typeof MATCHER_ELEMENT
+  | typeof MATCHER_ID
+  | typeof MATCHER_CLASS
+  | typeof MATCHER_ATTRIBUTE
+  | typeof MATCHER_PSEUDO
+  | typeof MATCHER_FUNCTION;
 
 export interface Part {
   combinator: Combinator;
@@ -44,10 +52,10 @@ export function querySelector(
   within: ParentNode,
   selector: string | Matcher[],
 ): Element | null {
-  const parts =
+  const parts: Part[] =
     typeof selector === 'string'
       ? parseSelector(selector)
-      : [{combinator: Combinator.Inner, matchers: selector}];
+      : [{combinator: COMBINATOR_INNER, matchers: selector}];
   let result: Element | null = null;
 
   const child = within[CHILD];
@@ -64,10 +72,10 @@ export function querySelectorAll(
   within: ParentNode,
   selector: string | Matcher[],
 ): Element[] {
-  const parts =
+  const parts: Part[] =
     typeof selector === 'string'
       ? parseSelector(selector)
-      : [{combinator: Combinator.Inner, matchers: selector}];
+      : [{combinator: COMBINATOR_INNER, matchers: selector}];
   const results: Element[] = [];
 
   const child = within[CHILD];
@@ -80,7 +88,7 @@ export function querySelectorAll(
 }
 
 export function parseSelector(selector: string) {
-  let part: Part = {combinator: Combinator.Inner, matchers: []};
+  let part: Part = {combinator: COMBINATOR_INNER, matchers: []};
   const parts = [part];
   const tokenizer =
     /\s*?([>\s+~]?)\s*?(?:(?:\[\s*([^\]=]+)(?:=(['"])(.*?)\3)?\s*\])|([#.]?)([^\s#.[>:+~]+)|:(\w+)(?:\((.*?)\))?)/gi;
@@ -95,27 +103,27 @@ export function parseSelector(selector: string) {
     // [8]: :function(argument) value
     if (token[1]) {
       // Update the combinator on the (now parent) Part:
-      if (token[1] === '>') part.combinator = Combinator.Child;
-      else if (token[1] === '+') part.combinator = Combinator.Adjacent;
-      else if (token[1] === '~') part.combinator = Combinator.Sibling;
-      else part.combinator = Combinator.Descendant;
+      if (token[1] === '>') part.combinator = COMBINATOR_CHILD;
+      else if (token[1] === '+') part.combinator = COMBINATOR_ADJACENT;
+      else if (token[1] === '~') part.combinator = COMBINATOR_SIBLING;
+      else part.combinator = COMBINATOR_DESCENDANT;
       // Add a new Part for the next selector parts:
-      part = {combinator: Combinator.Inner, matchers: []};
+      part = {combinator: COMBINATOR_INNER, matchers: []};
       parts.push(part);
     }
 
-    let type = MatcherType.Unknown;
+    let type: MatcherType = MATCHER_UNKNOWN;
     if (token[2]) {
-      type = MatcherType.Attribute;
+      type = MATCHER_ATTRIBUTE;
     } else if (token[5]) {
-      type = token[5] === '#' ? MatcherType.Id : MatcherType.Class;
+      type = token[5] === '#' ? MATCHER_ID : MATCHER_CLASS;
     } else if (token[7]) {
-      type = token[8] == null ? MatcherType.Pseudo : MatcherType.Function;
+      type = token[8] == null ? MATCHER_PSEUDO : MATCHER_FUNCTION;
     } else if (token[6]) {
       if (token[6] === '*') {
-        type = MatcherType.Unknown; // Universal selector matches all
+        type = MATCHER_UNKNOWN; // Universal selector matches all
       } else if (ELEMENT_SELECTOR_TEST.test(token[6])) {
-        type = MatcherType.Element;
+        type = MATCHER_ELEMENT;
       }
     }
     part.matchers.push({
@@ -159,21 +167,21 @@ function walkNodesForSelector(
 
 function matchesSelectorRecursive(element: Element, parts: Part[]): boolean {
   const {combinator, matchers} = parts[parts.length - 1]!;
-  if (combinator === Combinator.Inner) {
+  if (combinator === COMBINATOR_INNER) {
     if (!matchesSelectorMatcher(element, matchers)) return false;
     const pp = parts.slice(0, -1);
     return pp.length === 0 || matchesSelectorRecursive(element, pp);
   }
   const link =
-    combinator === Combinator.Child || combinator === Combinator.Descendant
+    combinator === COMBINATOR_CHILD || combinator === COMBINATOR_DESCENDANT
       ? PARENT
       : PREV;
   let ref = element[link];
   if (!ref) return false;
 
   if (
-    combinator === Combinator.Descendant ||
-    combinator === Combinator.Sibling
+    combinator === COMBINATOR_DESCENDANT ||
+    combinator === COMBINATOR_SIBLING
   ) {
     // For descendant/sibling combinators, search through all ancestors/siblings
     while (ref) {
@@ -188,7 +196,7 @@ function matchesSelectorRecursive(element: Element, parts: Part[]): boolean {
   } else {
     // For child/adjacent combinators, check only the immediate parent/sibling
     // For sibling combinators, skip non-element siblings
-    if (combinator === Combinator.Adjacent && !isElementNode(ref)) {
+    if (combinator === COMBINATOR_ADJACENT && !isElementNode(ref)) {
       // Skip to next element sibling
       while (ref && !isElementNode(ref)) {
         ref = ref[link];
@@ -205,18 +213,18 @@ function matchesSelectorRecursive(element: Element, parts: Part[]): boolean {
 }
 
 function matchesSelectorPart(element: Element, {combinator, matchers}: Part) {
-  if (combinator === Combinator.Inner) {
+  if (combinator === COMBINATOR_INNER) {
     return matchesSelectorMatcher(element, matchers);
   }
   const link =
-    combinator === Combinator.Child || combinator === Combinator.Descendant
+    combinator === COMBINATOR_CHILD || combinator === COMBINATOR_DESCENDANT
       ? PARENT
       : PREV;
   let ref = element[link];
   if (!ref) return false;
 
   // For sibling combinators, skip non-element siblings
-  if (combinator === Combinator.Adjacent && !isElementNode(ref)) {
+  if (combinator === COMBINATOR_ADJACENT && !isElementNode(ref)) {
     while (ref && !isElementNode(ref)) {
       ref = ref[link];
     }
@@ -228,8 +236,8 @@ function matchesSelectorPart(element: Element, {combinator, matchers}: Part) {
   }
 
   if (
-    combinator === Combinator.Descendant ||
-    combinator === Combinator.Sibling
+    combinator === COMBINATOR_DESCENDANT ||
+    combinator === COMBINATOR_SIBLING
   ) {
     while ((ref = ref[link])) {
       if (isElementNode(ref) && matchesSelectorMatcher(ref, matchers))
@@ -252,28 +260,28 @@ function matchesSelectorMatcher(
   }
   const {type, name, value} = matcher;
   switch (type) {
-    case MatcherType.Unknown:
+    case MATCHER_UNKNOWN:
       return name === '*'; // Universal selector
-    case MatcherType.Element:
-      return element.namespaceURI === NamespaceURI.XHTML
+    case MATCHER_ELEMENT:
+      return element.namespaceURI === HTML_NAMESPACE
         ? element.localName.toLowerCase() === name.toLowerCase()
         : element.localName === name;
-    case MatcherType.Id:
+    case MATCHER_ID:
       return element.getAttribute('id') === name;
-    case MatcherType.Class:
+    case MATCHER_CLASS:
       const classAttr = element.getAttribute('class');
       if (!classAttr) return false;
       return classAttr.split(/\s+/).includes(name);
-    case MatcherType.Attribute:
+    case MATCHER_ATTRIBUTE:
       return value == null
         ? element.hasAttribute(name)
         : element.getAttribute(name) === value;
-    case MatcherType.Pseudo:
+    case MATCHER_PSEUDO:
       switch (name) {
         default:
           throw Error(`Pseudo :${name} not implemented`);
       }
-    case MatcherType.Function:
+    case MATCHER_FUNCTION:
       switch (name) {
         case 'has':
           return matchesSelector(element, value || '');
diff --git a/packages/polyfill/source/serialization.ts b/packages/polyfill/source/serialization.ts
index 16bfde89..45bf55ad 100644
--- a/packages/polyfill/source/serialization.ts
+++ b/packages/polyfill/source/serialization.ts
@@ -5,7 +5,9 @@ import {
   NAME,
   NEXT,
   VALUE,
-  NodeType,
+  NODE_TYPE_COMMENT,
+  NODE_TYPE_ELEMENT,
+  NODE_TYPE_TEXT,
 } from './constants.ts';
 import type {Node} from './Node.ts';
 import type {Text} from './Text.ts';
@@ -71,7 +73,7 @@ export function serializeChildren(parentNode: ParentNode) {
 
 export function serializeNode(node: Node) {
   switch (node.nodeType) {
-    case NodeType.ELEMENT_NODE: {
+    case NODE_TYPE_ELEMENT: {
       const el = node as Element;
       let out = `<${el[NAME]}`;
       let attr = el[ATTRIBUTES]?.[CHILD];
@@ -94,14 +96,14 @@ export function serializeNode(node: Node) {
       out += `</${el[NAME]}>`;
       return out;
     }
-    case NodeType.TEXT_NODE: {
+    case NODE_TYPE_TEXT: {
       const text = node as Text;
       return text[DATA].replace(/&/g, '&amp;')
         .replace(/"/g, '&quot;')
         .replace(/</g, '&lt;')
         .replace(/>/g, '&gt;');
     }
-    case NodeType.COMMENT_NODE: {
+    case NODE_TYPE_COMMENT: {
       const text = node as Comment;
       return `<!--${text[DATA]}-->`;
     }
diff --git a/packages/polyfill/source/shared.ts b/packages/polyfill/source/shared.ts
index 65396b0c..6a334119 100644
--- a/packages/polyfill/source/shared.ts
+++ b/packages/polyfill/source/shared.ts
@@ -2,7 +2,10 @@ import {
   DATA,
   OWNER_DOCUMENT,
   ATTRIBUTES,
-  NodeType,
+  NODE_TYPE_COMMENT,
+  NODE_TYPE_DOCUMENT_FRAGMENT,
+  NODE_TYPE_ELEMENT,
+  NODE_TYPE_TEXT,
   CHILD,
   NEXT,
 } from './constants.ts';
@@ -14,26 +17,32 @@ import type {ParentNode} from './ParentNode.ts';
 import type {Element} from './Element.ts';
 import type {CharacterData} from './CharacterData.ts';
 import type {Text} from './Text.ts';
-import {querySelector, querySelectorAll, MatcherType} from './selectors.ts';
+import {
+  MATCHER_ELEMENT,
+  MATCHER_ID,
+  MATCHER_UNKNOWN,
+  querySelector,
+  querySelectorAll,
+} from './selectors.ts';
 
 export function isCharacterData(node: Node): node is CharacterData {
   return DATA in node;
 }
 
 export function isTextNode(node: Node): node is Text {
-  return node.nodeType === NodeType.TEXT_NODE;
+  return node.nodeType === NODE_TYPE_TEXT;
 }
 
 export function isCommentNode(node: Node): node is Comment {
-  return node.nodeType === NodeType.COMMENT_NODE;
+  return node.nodeType === NODE_TYPE_COMMENT;
 }
 
 export function isElementNode(node: Node): node is Element {
-  return node.nodeType === NodeType.ELEMENT_NODE;
+  return node.nodeType === NODE_TYPE_ELEMENT;
 }
 
 export function isDocumentFragmentNode(node: Node): node is DocumentFragment {
-  return node.nodeType === NodeType.DOCUMENT_FRAGMENT_NODE;
+  return node.nodeType === NODE_TYPE_DOCUMENT_FRAGMENT;
 }
 
 export function isParentNode(node: Node): node is ParentNode {
@@ -91,7 +100,7 @@ export function getElementById(within: ParentNode, elementId: string) {
   const id = String(elementId);
   if (id === '') return null;
 
-  return querySelector(within, [{type: MatcherType.Id, name: id}]);
+  return querySelector(within, [{type: MATCHER_ID, name: id}]);
 }
 
 export function getElementsByTagName(
@@ -101,7 +110,7 @@ export function getElementsByTagName(
   const name = String(qualifiedName);
 
   return querySelectorAll(within, [
-    {type: name === '*' ? MatcherType.Unknown : MatcherType.Element, name},
+    {type: name === '*' ? MATCHER_UNKNOWN : MATCHER_ELEMENT, name},
   ]);
 }
 
diff --git a/packages/polyfill/source/tests/constants.test.ts b/packages/polyfill/source/tests/constants.test.ts
new file mode 100644
index 00000000..500a08bf
--- /dev/null
+++ b/packages/polyfill/source/tests/constants.test.ts
@@ -0,0 +1,46 @@
+import {describe, expect, it} from 'vitest';
+
+import {Window} from '../index.ts';
+
+describe('DOM constants', () => {
+  it('exposes standard event phase constants', () => {
+    const {Event} = new Window();
+
+    expect(Event.NONE).toBe(0);
+    expect(Event.CAPTURING_PHASE).toBe(1);
+    expect(Event.AT_TARGET).toBe(2);
+    expect(Event.BUBBLING_PHASE).toBe(3);
+  });
+
+  it('initializes the event type', () => {
+    const {Event} = new Window();
+    const event = new Event('click');
+
+    expect(event.type).toBe('click');
+  });
+
+  it('uses standard node type values', () => {
+    const {document} = new Window();
+    const element = document.createElement('div');
+    element.setAttribute('example', 'value');
+
+    expect(element.nodeType).toBe(1);
+    expect(element.attributes.item(0)?.nodeType).toBe(2);
+    expect(document.createTextNode('').nodeType).toBe(3);
+    expect(document.createComment('').nodeType).toBe(8);
+    expect(document.nodeType).toBe(9);
+    expect(document.createDocumentFragment().nodeType).toBe(11);
+  });
+
+  it('uses standard namespace values', () => {
+    const {document} = new Window();
+
+    expect(document.createElement('div').namespaceURI).toBe(
+      'http://www.w3.org/1999/xhtml',
+    );
+    expect(
+      document.createElementNS('http://www.w3.org/2000/svg', 'svg')
+        .namespaceURI,
+    ).toBe('http://www.w3.org/2000/svg');
+  });
+});
diff --git a/packages/polyfill/source/tests/get-elements-by-tag-name.test.ts b/packages/polyfill/source/tests/get-elements-by-tag-name.test.ts
index 704d191b..2d8086af 100644
--- a/packages/polyfill/source/tests/get-elements-by-tag-name.test.ts
+++ b/packages/polyfill/source/tests/get-elements-by-tag-name.test.ts
@@ -1,4 +1,4 @@
-import {NamespaceURI} from '../constants.ts';
+import {SVG_NAMESPACE} from '../constants.ts';
 import {Window} from '../index.ts';
 
 import {beforeEach, describe, expect, it} from 'vitest';
@@ -26,11 +26,8 @@ describe('getElementsByTagName', () => {
   });
 
   it('matches non-HTML tag names case-sensitively', () => {
-    const svg = document.createElementNS(NamespaceURI.SVG, 'svg');
-    const gradient = document.createElementNS(
-      NamespaceURI.SVG,
-      'linearGradient',
-    );
+    const svg = document.createElementNS(SVG_NAMESPACE, 'svg');
+    const gradient = document.createElementNS(SVG_NAMESPACE, 'linearGradient');
     svg.appendChild(gradient);
     document.body.appendChild(svg);
 
diff --git a/packages/polyfill/source/tests/selectors.test.ts b/packages/polyfill/source/tests/selectors.test.ts
index bd9e5ff7..51303b93 100644
--- a/packages/polyfill/source/tests/selectors.test.ts
+++ b/packages/polyfill/source/tests/selectors.test.ts
@@ -1,12 +1,22 @@
 import {Window} from '../index.ts';
 import {
+  MATCHER_CLASS,
+  MATCHER_ELEMENT,
+  MATCHER_ID,
+  MATCHER_UNKNOWN,
   parseSelector,
   querySelector,
   querySelectorAll,
-  MatcherType,
 } from '../selectors.ts';
 import type {ParentNode} from '../ParentNode.ts';
 
+const MatcherType = {
+  Unknown: MATCHER_UNKNOWN,
+  Element: MATCHER_ELEMENT,
+  Id: MATCHER_ID,
+  Class: MATCHER_CLASS,
+} as const;
+
 import {describe, it, expect, beforeEach} from 'vitest';
 
 describe('selector parsing and matching', () => {