diff --git a/src/lib/components/Navigation.svelte b/src/lib/components/Navigation.svelte
index aea097fa..32f408f3 100644
--- a/src/lib/components/Navigation.svelte
+++ b/src/lib/components/Navigation.svelte
@@ -1,5 +1,5 @@
 <script>
-  import {serialPort, syncing} from "$lib/serial/connection.js"
+  import {serialPort, syncing} from "$lib/serial/connection"
   import {browser} from "$app/environment"
   import {page} from "$app/stores"
 </script>
diff --git a/src/lib/components/RingInput.svelte b/src/lib/components/RingInput.svelte
index dfecea3a..be6b63e5 100644
--- a/src/lib/components/RingInput.svelte
+++ b/src/lib/components/RingInput.svelte
@@ -1,43 +1,32 @@
-<script>
-  import {layout} from "$lib/serial/connection.js"
-  import {KEYMAP_CODES} from "$lib/serial/keymap-codes.js"
+<script lang="ts">
+  import {layout} from "$lib/serial/connection"
+  import type {CharaLayout} from "$lib/serial/connection"
+  import {KEYMAP_CODES} from "$lib/serial/keymap-codes"
+  import type {KeyInfo} from "$lib/serial/keymap-codes"
 
   export let activeLayer = 0
-
-  /** @type {{d: number, n: number, w: number, e: number, s: number}} */
-  export let keys
-
-  /** @type {'primary' | 'secondary' | 'tertiary'} */
-  export let type = "primary"
+  export let keys: Record<"d" | "n" | "w" | "e", number>
+  export let type: "primary" | "secondary" | "tertiary" = "primary"
 
   const layerNames = ["Primary Layer", "Number Layer", "Function Layer"]
 
   const virtualLayerMap = [1, 0, 2]
   const characterOffset = 8
 
-  function offsetDistance(quadrant, layer, activeLayer) {
+  function offsetDistance(quadrant: number, layer: number, activeLayer: number): number {
     const layerOffsetIndex = virtualLayerMap[layer] - virtualLayerMap[activeLayer]
     const layerOffset = quadrant > 2 ? -characterOffset : characterOffset
     return 25 * quadrant + layerOffsetIndex * layerOffset
   }
 
-  /**
-   * @param keys {import('$lib/serial/keymap.js').KeyInfo[]}
-   * @returns {*}
-   */
-  function getKeyDescriptions(keys) {
+  function getKeyDescriptions(keys: KeyInfo[]): string {
     return keys.map(({title, id, code}, i) => `${title || id || code} (${layerNames[i]})`).join("\n")
   }
 
-  /**
-   * @param id {number}
-   * @param layout {[number[], number[], number[]]}
-   * @returns import('$lib/serial/keymap.js').KeyInfo[]
-   */
-  function getActions(id, layout) {
+  function getActions(id: number, layout: CharaLayout): KeyInfo[] {
     return Array.from({length: 3}).map((_, i) => {
       const actionId = layout?.[i][id]
-      return actionId !== undefined ? KEYMAP_CODES[actionId] : {code: actionId}
+      return KEYMAP_CODES[actionId]
     })
   }
 </script>
diff --git a/src/lib/components/Terminal.svelte b/src/lib/components/Terminal.svelte
index 7b0f4ddd..a52847d4 100644
--- a/src/lib/components/Terminal.svelte
+++ b/src/lib/components/Terminal.svelte
@@ -1,22 +1,16 @@
-<script>
-  import {serialLog, serialPort} from "$lib/serial/connection.js"
+<script lang="ts">
+  import {serialLog, serialPort} from "$lib/serial/connection"
   import {slide} from "svelte/transition"
 
-  /**
-   * @param event {InputEvent}
-   */
-  function submit(event) {
+  function submit(event: InputEvent) {
     event.preventDefault()
     $serialPort.send(value.trim())
     value = ""
     io.scrollTo({top: io.scrollHeight})
   }
 
-  /** @type {string} */
-  let value
-
-  /** @type {HTMLDivElement} */
-  let io
+  let value: string
+  let io: HTMLDivElement
 
   export let resizable = false
 </script>
diff --git a/src/lib/icons.js b/src/lib/icons.js
deleted file mode 100644
index 5a42d295..00000000
--- a/src/lib/icons.js
+++ /dev/null
@@ -1,3 +0,0 @@
-export const Icon = {
-  close: 0xe5cd,
-}
diff --git a/src/lib/serial/connection.js b/src/lib/serial/connection.ts
similarity index 52%
rename from src/lib/serial/connection.js
rename to src/lib/serial/connection.ts
index 09720113..327546c7 100644
--- a/src/lib/serial/connection.js
+++ b/src/lib/serial/connection.ts
@@ -1,19 +1,26 @@
 import {writable} from "svelte/store"
-import {CharaDevice} from "$lib/serial/device.js"
+import {CharaDevice} from "$lib/serial/device"
 
-/** @type {import('svelte/store').Writable<import('./device.js').CharaDevice>} */
-export const serialPort = writable()
+export const serialPort = writable<CharaDevice>()
 
-/** @type {import('svelte/store').Writable<Array<{type: 'input' | 'output' | 'system'; value: string}>>} */
-export const serialLog = writable([])
+export interface SerialLogEntry {
+  type: "input" | "output" | "system"
+  value: string
+}
 
-/** @type {import('svelte/store').Writable<Array<{actions: number[]; phrase: string}>>} */
-export const chords = writable([])
+export const serialLog = writable<SerialLogEntry[]>([])
 
-/** @type {import('svelte/store').Writable<[number[], number[], number[]]>} */
-export const layout = writable([[], [], []])
+export interface Chord {
+  actions: number[]
+  phrase: string
+}
+
+export const chords = writable<Chord[]>([])
+
+export type CharaLayout = [number[], number[], number[]]
+
+export const layout = writable<CharaLayout>([[], [], []])
 
-/** @type {import('svelte/store').Writable<boolean>} */
 export const syncing = writable(false)
 
 /** @type {CharaDevice} */
@@ -24,7 +31,7 @@ export async function initSerial() {
   device ??= new CharaDevice()
   serialPort.set(device)
 
-  const parsedLayout = [[], [], []]
+  const parsedLayout: CharaLayout = [[], [], []]
   for (let layer = 1; layer <= 3; layer++) {
     for (let i = 0; i < 90; i++) {
       parsedLayout[layer - 1][i] = await device.getLayoutKey(layer, i)
diff --git a/src/lib/serial/device.js b/src/lib/serial/device.ts
similarity index 53%
rename from src/lib/serial/device.js
rename to src/lib/serial/device.ts
index 5cbfc1a4..4eca5c8e 100644
--- a/src/lib/serial/device.js
+++ b/src/lib/serial/device.ts
@@ -1,5 +1,6 @@
-import {LineBreakTransformer} from "$lib/serial/line-break-transformer.js"
-import {serialLog} from "$lib/serial/connection.js"
+import {LineBreakTransformer} from "$lib/serial/line-break-transformer"
+import {serialLog} from "$lib/serial/connection"
+import type {Chord} from "$lib/serial/connection"
 
 export const VENDOR_ID = 0x239a
 
@@ -11,29 +12,22 @@ export async function hasSerialPermission() {
 }
 
 export class CharaDevice {
-  /** @type {Promise<SerialPort>} */
-  #port
-  /** @type {Promise<ReadableStreamDefaultReader<string>>} */
-  #reader
+  private readonly port: Promise<SerialPort>
+  private readonly reader: Promise<ReadableStreamDefaultReader<string>>
 
-  #encoder = new TextEncoder()
+  private readonly abortController1 = new AbortController()
+  private readonly abortController2 = new AbortController()
 
-  #abortController1 = new AbortController()
-  #abortController2 = new AbortController()
+  private lock?: Promise<true>
 
-  /** @type {Promise<true> | undefined} */
-  #lock
-
-  /** @type {Promise<string>} */
-  version
-  /** @type {Promise<string>} */
-  deviceId
+  version: Promise<string>
+  deviceId: Promise<string>
 
   /**
    * @param baudRate
    */
   constructor(baudRate = 115200) {
-    this.#port = navigator.serial.getPorts().then(async ports => {
+    this.port = navigator.serial.getPorts().then(async ports => {
       const port =
         ports.find(it => it.getInfo().usbVendorId === VENDOR_ID) ??
         (await navigator.serial.requestPort({filters: [{usbVendorId: VENDOR_ID}]}))
@@ -42,7 +36,7 @@ export class CharaDevice {
       serialLog.update(it => {
         it.push({
           type: "system",
-          value: `Connected; ID: 0x${info.usbProductId.toString(16)}; Vendor: 0x${info.usbVendorId.toString(
+          value: `Connected; ID: 0x${info.usbProductId?.toString(16)}; Vendor: 0x${info.usbVendorId?.toString(
             16,
           )}`,
         })
@@ -50,29 +44,27 @@ export class CharaDevice {
       })
       return port
     })
-    this.#reader = this.#port.then(async port => {
+    this.reader = this.port.then(async port => {
       const decoderStream = new TextDecoderStream()
-      void port.readable.pipeTo(decoderStream.writable, {signal: this.#abortController1.signal})
+      void port.readable!.pipeTo(decoderStream.writable, {signal: this.abortController1.signal})
 
-      return decoderStream.readable
-        .pipeThrough(new TransformStream(new LineBreakTransformer()), {signal: this.#abortController2.signal})
+      return decoderStream
+        .readable!.pipeThrough(new TransformStream(new LineBreakTransformer()), {
+          signal: this.abortController2.signal,
+        })
         .getReader()
     })
-    this.#lock = this.#reader.then(() => {
-      this.#lock = undefined
+    this.lock = this.reader.then(() => {
+      delete this.lock
       return true
     })
     this.version = this.send("VERSION")
     this.deviceId = this.send("ID")
   }
 
-  /**
-   * @returns {Promise<string>}
-   */
-  async #read() {
-    return this.#reader.then(async it => {
-      /** @type {string} */
-      const result = await it.read().then(({value}) => value)
+  private async internalRead() {
+    return this.reader.then(async it => {
+      const result: string = await it.read().then(({value}) => value!)
       serialLog.update(it => {
         it.push({
           type: "output",
@@ -86,12 +78,10 @@ export class CharaDevice {
 
   /**
    * Send a command to the device
-   * @param command {string}
-   * @returns {Promise<void>}
    */
-  async #send(...command) {
-    const port = await this.#port
-    const writer = port.writable.getWriter()
+  private async internalSend(...command: string[]) {
+    const port = await this.port
+    const writer = port.writable!.getWriter()
     try {
       serialLog.update(it => {
         it.push({
@@ -108,35 +98,32 @@ export class CharaDevice {
 
   /**
    * Read/write to serial port
-   * @template T
-   * @param callback {(send: (...commands: string) => Promise<void>, read: () => Promise<string>) => T | Promise<T>}
-   * @returns Promise<T>
    */
-  async runWith(callback) {
-    while (this.#lock) {
-      await this.#lock
+  async runWith<T>(
+    callback: (send: typeof this.internalSend, read: typeof this.internalRead) => T | Promise<T>,
+  ): Promise<T> {
+    while (this.lock) {
+      await this.lock
     }
-    const send = this.#send.bind(this)
-    const read = this.#read.bind(this)
-    const exec = new Promise(async resolve => {
-      let result
+    const send = this.internalSend.bind(this)
+    const read = this.internalRead.bind(this)
+    const exec = new Promise<T>(async resolve => {
+      let result!: T
       try {
         result = await callback(send, read)
       } finally {
-        this.#lock = undefined
+        this.lock = undefined
         resolve(result)
       }
     })
-    this.#lock = exec.then(() => true)
+    this.lock = exec.then(() => true)
     return exec
   }
 
   /**
    * Send to serial port
-   * @param command {string}
-   * @returns Promise<string>
    */
-  async send(...command) {
+  async send(...command: string[]) {
     return this.runWith(async (send, read) => {
       await send(...command)
       const commandString = command.join(" ").replace(/[-[\]{}()*+?.,\\^$|#\s]/g, "\\$&")
@@ -144,20 +131,13 @@ export class CharaDevice {
     })
   }
 
-  /**
-   * @returns {Promise<number>}
-   */
-  async getChordCount() {
+  async getChordCount(): Promise<number> {
     return Number.parseInt(await this.send("CML C0"))
   }
 
-  /**
-   * @param index {number}
-   * @returns {Promise<{actions: number[]; phrase: string, unk: number}>}
-   */
-  async getChord(index) {
+  async getChord(index: number): Promise<Chord> {
     const chord = await this.send(`CML C1 ${index}`)
-    const [keys, rawPhrase, b] = chord.split(" ")
+    const [keys, rawPhrase] = chord.split(" ")
     let phrase = []
     for (let i = 0; i < rawPhrase.length; i += 2) {
       phrase.push(Number.parseInt(rawPhrase.substring(i, i + 2), 16))
@@ -175,16 +155,10 @@ export class CharaDevice {
     return {
       actions,
       phrase: String.fromCodePoint(...phrase),
-      unk: Number(b),
     }
   }
 
-  /**
-   * @param layer {number}
-   * @param id {number}
-   * @returns {Promise<number>}
-   */
-  async getLayoutKey(layer, id) {
+  async getLayoutKey(layer: number, id: number) {
     const layout = await this.send(`VAR B3 A${layer} ${id}`)
     const [position] = layout.split(" ").map(Number)
     return position
diff --git a/src/lib/serial/keymap-codes.js b/src/lib/serial/keymap-codes.js
deleted file mode 100644
index 2bee31a4..00000000
--- a/src/lib/serial/keymap-codes.js
+++ /dev/null
@@ -1,17 +0,0 @@
-import keymapCodes from "$lib/assets/keymap_codes.json"
-import keySymbols from "$lib/assets/key-symbols.json"
-
-/** @type {Record<number, import('./keymap.js').KeyInfo>} */
-export const KEYMAP_CODES = Object.fromEntries(
-  keymapCodes.map(([code, charset, id, title, description]) => [
-    code,
-    {
-      code: Number(code),
-      title: title || undefined,
-      charset: charset || undefined,
-      id: id || undefined,
-      symbol: id ? keySymbols[id] || undefined : undefined,
-      description: description || undefined,
-    },
-  ]),
-)
diff --git a/src/lib/serial/keymap.d.ts b/src/lib/serial/keymap-codes.ts
similarity index 59%
rename from src/lib/serial/keymap.d.ts
rename to src/lib/serial/keymap-codes.ts
index be09db9e..5475d0fb 100644
--- a/src/lib/serial/keymap.d.ts
+++ b/src/lib/serial/keymap-codes.ts
@@ -1,3 +1,6 @@
+import keymapCodes from "$lib/assets/keymap_codes.json"
+import keySymbols from "$lib/assets/key-symbols.json"
+
 export interface KeyInfo {
   /**
    * Numeric action code
@@ -45,3 +48,17 @@ export type CharsetCategory =
   | "Keybard"
   | "CharaChorder"
   | "CharaChorder One"
+
+export const KEYMAP_CODES: Record<number, KeyInfo> = Object.fromEntries(
+  keymapCodes.map(([code, charset, id, title, description]) => [
+    code,
+    {
+      code: Number(code),
+      title: title || undefined,
+      charset: (charset || undefined) as CharsetCategory,
+      id: id || undefined,
+      symbol: id ? keySymbols[id as keyof typeof keySymbols] || undefined : undefined,
+      description: description || undefined,
+    },
+  ]),
+)
diff --git a/src/lib/serial/line-break-transformer.js b/src/lib/serial/line-break-transformer.ts
similarity index 62%
rename from src/lib/serial/line-break-transformer.js
rename to src/lib/serial/line-break-transformer.ts
index 36c6bad7..473d447d 100644
--- a/src/lib/serial/line-break-transformer.js
+++ b/src/lib/serial/line-break-transformer.ts
@@ -1,21 +1,18 @@
-// @ts-check
 export class LineBreakTransformer {
-  constructor() {
-    this.chunks = ""
-  }
+  private chunks = ""
 
   // noinspection JSUnusedGlobalSymbols
-  transform(chunk, controller) {
+  transform(chunk: string, controller: TransformStreamDefaultController) {
     this.chunks += chunk
     const lines = this.chunks.split("\r\n")
-    this.chunks = lines.pop()
+    this.chunks = lines.pop()!
     for (const line of lines) {
       controller.enqueue(line)
     }
   }
 
   // noinspection JSUnusedGlobalSymbols
-  flush(controller) {
+  flush(controller: TransformStreamDefaultController) {
     controller.enqueue(this.chunks)
   }
 }
diff --git a/src/routes/+layout.server.js b/src/routes/+layout.server.js
deleted file mode 100644
index 3cf134e9..00000000
--- a/src/routes/+layout.server.js
+++ /dev/null
@@ -1,10 +0,0 @@
-import {themeBase, themeColor, themeSuccessBase} from "$lib/style/theme.server.js"
-
-/** @type {import("./$types").LayoutServerLoad} */
-export async function load() {
-  return {
-    themeSuccessBase,
-    themeBase,
-    themeColor,
-  }
-}
diff --git a/src/routes/+layout.server.ts b/src/routes/+layout.server.ts
new file mode 100644
index 00000000..b4fef69b
--- /dev/null
+++ b/src/routes/+layout.server.ts
@@ -0,0 +1,8 @@
+import {themeBase, themeColor, themeSuccessBase} from "$lib/style/theme.server"
+import type {LayoutServerLoad} from "./$types"
+
+export const load = (async () => ({
+  themeSuccessBase,
+  themeBase,
+  themeColor,
+})) satisfies LayoutServerLoad
diff --git a/src/routes/+layout.svelte b/src/routes/+layout.svelte
index ca55c790..5b52648c 100644
--- a/src/routes/+layout.svelte
+++ b/src/routes/+layout.svelte
@@ -1,15 +1,17 @@
-<script>
+<script lang="ts">
   import "$lib/fonts/noto-sans-mono.scss"
   import "$lib/fonts/material-symbols-rounded.scss"
   import {onMount} from "svelte"
   import {applyTheme, argbFromHex, themeFromSourceColor} from "@material/material-color-utilities"
   import Navigation from "$lib/components/Navigation.svelte"
-  import {hasSerialPermission} from "$lib/serial/device.js"
-  import {initSerial} from "$lib/serial/connection.js"
+  import {hasSerialPermission} from "$lib/serial/device"
+  import {initSerial} from "$lib/serial/connection"
+  // noinspection TypeScriptCheckImport
   import {pwaInfo} from "virtual:pwa-info"
+  import type {LayoutServerData} from "./$types"
+  import type {RegisterSWOptions} from "vite-plugin-pwa/types"
 
-  /** @type {import('./$types').LayoutServerData} */
-  export let data
+  export let data: LayoutServerData
 
   onMount(async () => {
     const theme = themeFromSourceColor(argbFromHex("#6D81C7"), [
@@ -19,15 +21,14 @@
     applyTheme(theme, {target: document.body, dark})
 
     if (pwaInfo) {
-      /** @type {import('vite-plugin-pwa/types').RegisterSWOptions} */
-      const swOptions = {
+      // noinspection TypeScriptCheckImport
+      const {registerSW} = await import("virtual:pwa-register")
+      registerSW({
         immediate: true,
         onRegisterError(error) {
           console.log("ServiceWorker Registration Error", error)
         },
-      }
-      const {registerSW} = await import("virtual:pwa-register")
-      registerSW(swOptions)
+      } satisfies RegisterSWOptions)
     }
 
     if (await hasSerialPermission()) await initSerial()
diff --git a/src/routes/+layout.js b/src/routes/+layout.ts
similarity index 98%
rename from src/routes/+layout.js
rename to src/routes/+layout.ts
index 51a392bc..aaf46e44 100644
--- a/src/routes/+layout.js
+++ b/src/routes/+layout.ts
@@ -1,3 +1,2 @@
 export const prerender = true
-
 export const trailingSlash = "always"
diff --git a/src/routes/+page.js b/src/routes/+page.js
deleted file mode 100644
index 15a1c3aa..00000000
--- a/src/routes/+page.js
+++ /dev/null
@@ -1,6 +0,0 @@
-import {redirect} from "@sveltejs/kit"
-
-/** @type {import("./$types").PageLoad} */
-export function load() {
-  throw redirect(302, "/config/")
-}
diff --git a/src/routes/+page.ts b/src/routes/+page.ts
new file mode 100644
index 00000000..2c36f17c
--- /dev/null
+++ b/src/routes/+page.ts
@@ -0,0 +1,6 @@
+import {redirect} from "@sveltejs/kit"
+import type {PageLoad} from "./$types"
+
+export const load = (() => {
+  throw redirect(302, "/config/")
+}) satisfies PageLoad
diff --git a/src/routes/config/+page.js b/src/routes/config/+page.js
deleted file mode 100644
index 91037b00..00000000
--- a/src/routes/config/+page.js
+++ /dev/null
@@ -1,6 +0,0 @@
-import {redirect} from "@sveltejs/kit"
-
-/** @type {import("./$types").PageLoad} */
-export function load() {
-  throw redirect(302, "/config/chords/")
-}
diff --git a/src/routes/config/+page.ts b/src/routes/config/+page.ts
new file mode 100644
index 00000000..56719f12
--- /dev/null
+++ b/src/routes/config/+page.ts
@@ -0,0 +1,6 @@
+import {redirect} from "@sveltejs/kit"
+import type {PageLoad} from "./$types"
+
+export const load = (() => {
+  throw redirect(302, "/config/chords/")
+}) satisfies PageLoad
diff --git a/src/routes/config/chords/+page.svelte b/src/routes/config/chords/+page.svelte
index 18e20db8..a8a0df77 100644
--- a/src/routes/config/chords/+page.svelte
+++ b/src/routes/config/chords/+page.svelte
@@ -1,6 +1,6 @@
-<script>
-  import {chords} from "$lib/serial/connection.js"
-  import {KEYMAP_CODES} from "$lib/serial/keymap-codes.js"
+<script lang="ts">
+  import {chords} from "$lib/serial/connection"
+  import {KEYMAP_CODES} from "$lib/serial/keymap-codes"
 </script>
 
 <svelte:head>
diff --git a/jsconfig.json b/tsconfig.json
similarity index 100%
rename from jsconfig.json
rename to tsconfig.json