diff --git a/index.ts b/index.ts
new file mode 100644
index 0000000..b7bf294
--- /dev/null
+++ b/index.ts
@@ -0,0 +1,7 @@
+export { Level, type Options } from 'types'
+export * as Writer from 'writer'
+export {set_options, get_options, set_writer, get_writer, remove_writer, Logger} from 'index'
+
+import {Logger} from 'index'
+
+export default (namespace: string) => new Logger(namespace)
diff --git a/src/index.ts b/src/index.ts
new file mode 100644
index 0000000..139d109
--- /dev/null
+++ b/src/index.ts
@@ -0,0 +1,75 @@
+import {Level, level_to_string, type Options} from 'types'
+import {Writer} from 'writer'
+
+export const writers = new Map<string, Writer>
+export let options: Options = {
+    format: "[$time] $level $namespace :",
+}
+
+export function set_options(opt: Partial<Options>) {
+    options = {...options, ...opt}
+}
+export function get_options() : Readonly<Options> {
+    return options
+}
+
+export function set_writer(name: string, writer: Writer) {
+    writers.set(name, writer)
+}
+export function get_writer(name: string) : Readonly<Writer> | undefined {
+    return writers.get(name)
+}
+export function remove_writer(name: string) : boolean {
+    return writers.delete(name)
+}
+
+export class Logger {
+    private readonly _namespace: string
+
+    constructor(namespace: string) {
+        this._namespace = namespace
+    }
+
+    public get namespace() : string {
+        return this._namespace
+    }
+
+    public extend(sub_namespace: string) : Logger {
+        return new Logger(`${this.namespace}:${sub_namespace}`)
+    }
+
+    public debug(...data: any[]) : void {
+        log(data, Level.DEBUG, this._namespace)
+    }
+
+    public trace(...data: any[]) : void {
+        log(data, Level.TRACE, this._namespace)
+    }
+
+    public info(...data: any[]) : void {
+        log(data, Level.INFO, this._namespace)
+    }
+
+    public warn(...data: any[]) : void {
+        log(data, Level.WARNING, this._namespace)
+    }
+
+    public error(...data: any[]) : void {
+        log(data, Level.ERROR, this._namespace)
+    }
+}
+
+function log(message: any[], level: Level, namespace: string) : void {
+    if (writers.size === 0) return
+
+    // Format header of log
+    const head = options.format
+        .replace("$time", new Date().toISOString())
+        .replace("$namespace", namespace)
+    const head_bw = head.replace('$level', level_to_string(level, false))
+    const head_color = head.replace("$level", level_to_string(level, true))
+
+    for (const writer of writers.values()) {
+        writer.log(level, writer.options.with_color ? head_color : head_bw, ...message)
+    }
+}
diff --git a/src/types.ts b/src/types.ts
new file mode 100644
index 0000000..fdaf5f9
--- /dev/null
+++ b/src/types.ts
@@ -0,0 +1,59 @@
+import { Chalk } from 'chalk'
+
+export type Options = {
+    format: string,
+}
+
+export enum Level {
+    DEBUG = 0,
+    TRACE = 1,
+    INFO = 2,
+    WARNING = 3,
+    ERROR = 4,
+}
+
+export enum LevelFilter {
+    DEBUG = 0,
+    TRACE = 1,
+    INFO = 2,
+    WARNING = 3,
+    ERROR = 4,
+    OFF = 6,
+}
+
+export type WriterOptions = {
+    minLevel: Level,
+    with_color: boolean,
+    [key: string | number | symbol]: any,
+}
+
+export function level_to_string(level: Level, with_color: boolean) : string {
+    const str = get_string(level)
+
+    if (!with_color) return str
+
+    const color = get_color(level)
+    return color(str)
+}
+
+function get_string(level: Level) : string {
+    switch (level) {
+        case Level.DEBUG: return "DEBUG  "
+        case Level.TRACE: return "TRACE  "
+        case Level.INFO: return "INFO   "
+        case Level.WARNING: return "WARNING"
+        case Level.ERROR: return "ERROR  "
+    }
+}
+
+const chalk = new Chalk({ level: 2 }) // 256 colors
+
+function get_color(level: Level) {
+    switch (level) {
+        case Level.DEBUG: return chalk.blueBright
+        case Level.TRACE: return chalk.green
+        case Level.INFO: return (str: string) => str
+        case Level.WARNING: return chalk.hex('#FFA500')
+        case Level.ERROR: return chalk.red
+    }
+}
diff --git a/src/writer/console.ts b/src/writer/console.ts
new file mode 100644
index 0000000..309a6c6
--- /dev/null
+++ b/src/writer/console.ts
@@ -0,0 +1,18 @@
+import {Writer} from 'writer'
+import {Level} from 'types'
+
+export class Console extends Writer {
+    protected write(level: Level, ...data: any[]) : void {
+        Console.get_logger(level)(...data)
+    }
+
+    private static get_logger(level: Level) {
+        switch (level) {
+            case Level.DEBUG: return console.debug
+            case Level.TRACE: return console.debug
+            case Level.INFO: return console.log
+            case Level.WARNING: return console.warn
+            case Level.ERROR: return console.error
+        }
+    }
+}
diff --git a/src/writer/counter.ts b/src/writer/counter.ts
new file mode 100644
index 0000000..11ff0b4
--- /dev/null
+++ b/src/writer/counter.ts
@@ -0,0 +1,30 @@
+import {Writer} from 'writer'
+import {Level} from 'types'
+
+export class Counter extends Writer {
+    private readonly calls = {
+        debug: 0,
+        trace: 0,
+        info: 0,
+        warn: 0,
+        error: 0,
+    }
+
+    public constructor() {
+        super({minLevel: Level.DEBUG, with_color: false});
+    }
+
+    protected write(level: Level, ...data: any[]): void {
+        switch (level) {
+            case Level.DEBUG: this.calls.debug++; break
+            case Level.TRACE: this.calls.trace++; break
+            case Level.INFO: this.calls.info++; break
+            case Level.WARNING: this.calls.warn++; break
+            case Level.ERROR: this.calls.error++; break
+        }
+    }
+
+    public get count() {
+        return this.calls
+    }
+}
diff --git a/src/writer/file.ts b/src/writer/file.ts
new file mode 100644
index 0000000..aa154f8
--- /dev/null
+++ b/src/writer/file.ts
@@ -0,0 +1,43 @@
+import {Writer} from 'writer'
+import {type WriterOptions, Level} from 'types'
+
+export class File extends Writer {
+    public constructor(options: WriterOptions & { path: string }) {
+        const {path, ...rest} = options
+        super(rest)
+    }
+
+    protected write(level: Level, ...data: any[]) : void {
+        // TODO
+    }
+}
+
+export class DailyFile extends Writer {
+    private _writer: File
+    private readonly _folder: string
+    private now: Date = new Date()
+
+    public constructor(options: WriterOptions & {folder: string}) {
+        const {folder, ...rest} = options
+
+        super(rest)
+        this._folder = folder
+
+        this._writer = DailyFile.start(this.options, this._folder, this.now)
+    }
+
+    private static start(options: WriterOptions, folder: string, now: Date) : File {
+        const date = now.toISOString().split('T')[0]
+        const path = `${folder}/${date}.log`
+        return new File({...options, path})
+    }
+
+    protected write(level: Level, ...data: any[]): void {
+        if (new Date().getDay() !== this.now.getDay()) {
+            this.now = new Date()
+            this._writer = DailyFile.start(this.options, this._folder, this.now)
+        }
+
+        return this._writer.log(level, data)
+    }
+}
diff --git a/src/writer/index.ts b/src/writer/index.ts
new file mode 100644
index 0000000..ff32f5a
--- /dev/null
+++ b/src/writer/index.ts
@@ -0,0 +1,22 @@
+export {Console} from 'writer/console'
+export {File} from 'writer/file'
+export {Counter} from 'writer/counter'
+
+import {Level, type WriterOptions} from 'types'
+
+export abstract class Writer {
+    protected readonly _options: WriterOptions;
+    protected constructor(options: WriterOptions) {
+        this._options = options
+    }
+
+    public log(level: Level, ...data: any[]) : void {
+        if (level < this.options.minLevel) return
+        this.write(level, ...data)
+    }
+    protected abstract write(level: Level, ...data: any[]) : void;
+
+    public get options() : WriterOptions {
+        return this._options
+    }
+}
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