diff --git a/Sources/phbar/AppDelegate.swift b/Sources/phbar/AppDelegate.swift
new file mode 100644
index 0000000..24786f7
--- /dev/null
+++ b/Sources/phbar/AppDelegate.swift
@@ -0,0 +1,23 @@
+import AppKit
+
+@MainActor
+final class AppDelegate: NSObject, NSApplicationDelegate {
+	var barController: PHController!
+	var window: BarWindow!
+
+	init(screen: NSScreen, blocks: [PHBlock]) {
+		super.init()
+
+		self.barController = PHController(screen: screen, blocks: blocks)
+	}
+
+	func applicationDidFinishLaunching(_ notification: Notification) {
+		window = BarWindow(controller: barController)
+		window.orderFront(nil)
+		barController.startAutoRefresh()
+	}
+
+	func applicationWillTerminate(_ notification: Notification) {
+		barController.stopAutoRefresh()
+	}
+}
diff --git a/Sources/phbar/CLI/cli+start.swift b/Sources/phbar/CLI/cli+start.swift
new file mode 100644
index 0000000..aa5848c
--- /dev/null
+++ b/Sources/phbar/CLI/cli+start.swift
@@ -0,0 +1,55 @@
+import AppKit
+import ArgumentParser
+import Foundation
+
+extension phbar {
+	struct start: ParsableCommand {
+		static let configuration = CommandConfiguration(
+			commandName: "start",
+			abstract: "Start the status bar."
+		)
+
+		mutating func run() throws {
+			let screen = try targetScreen(monitor: 0)
+
+			// NOTE: Make sure NSApp.run() runs in the main thread
+			dispatchPrecondition(condition: .onQueue(.main))
+
+			try MainActor.assumeIsolated {
+				let blocks = try PHBlock.load()
+
+				let delegate = AppDelegate(screen: screen, blocks: blocks)
+				let app = NSApplication.shared
+				app.setActivationPolicy(.accessory)
+				app.delegate = delegate
+				app.run()
+
+				throw ExitCode.success
+			}
+		}
+	}
+}
+
+// Monitor
+
+extension phbar.start {
+	private func targetScreen(monitor: Int) throws -> NSScreen {
+		let screens = NSScreen.screens
+		guard !screens.isEmpty else { throw CleanExit.message("No monitor founded") }
+
+		if monitor >= 0, monitor < screens.count {
+			return screens[monitor]
+		}
+
+		// Default: screen containing the mouse cursor
+		let mouseLocation = NSEvent.mouseLocation
+		guard
+			let screen = screens.first(where: { NSMouseInRect(mouseLocation, $0.frame, false) })
+				?? screens.first
+		else {
+			throw CleanExit.message("No monitor founded")
+		}
+
+		return screen
+	}
+}
diff --git a/Sources/phbar/Controllers/PHController.swift b/Sources/phbar/Controllers/PHController.swift
new file mode 100644
index 0000000..1124e4b
--- /dev/null
+++ b/Sources/phbar/Controllers/PHController.swift
@@ -0,0 +1,36 @@
+import SwiftUI
+
+@MainActor
+final class PHController: ObservableObject {
+	let screen: NSScreen
+	@Published var blocks: [PHBlock]
+
+	init(screen: NSScreen, blocks: [PHBlock]) {
+		self.screen = screen
+		self.blocks = blocks
+	}
+
+	// MARK: - Refresh
+
+	/// Start auto-refresh for every block.
+	func startAutoRefresh() {
+		for block in blocks {
+			block.startAutoRefresh()
+		}
+	}
+
+	/// Stop auto-refresh for every block.
+	func stopAutoRefresh() {
+		for block in blocks {
+			block.stopAutoRefresh()
+		}
+	}
+
+	/// Force every block to recompute its label immediately (manual refresh).
+	/// Each block updates concurrently; the view refreshes as results arrive.
+	func refresh() {
+		for block in blocks {
+			Task { await block.update() }
+		}
+	}
+}
diff --git a/Sources/phbar/Models/PHBlock.swift b/Sources/phbar/Models/PHBlock.swift
new file mode 100644
index 0000000..7105468
--- /dev/null
+++ b/Sources/phbar/Models/PHBlock.swift
@@ -0,0 +1,148 @@
+import ArgumentParser
+import Foundation
+import SwiftUI
+import TOML
+
+@MainActor
+final class PHBlock: ObservableObject, Decodable, Identifiable {
+	let id = UUID()
+	let command: String
+	let name: String?
+	let style: String?
+	let refresh: Double?
+
+	@Published private(set) var label = ""
+
+	/// The repeating refresh task, if any.
+	private var refreshTask: Task<Void, Never>?
+
+	private enum CodingKeys: String, CodingKey {
+		case command, name, style, refresh
+	}
+
+	deinit {
+		refreshTask?.cancel()
+	}
+
+	// MARK: - Refresh
+
+	/// Start keeping the label up to date.
+	///
+	/// The label is always recomputed immediately. When `refresh` is set to a
+	/// positive number of seconds, it is then recomputed on that interval until
+	/// `stopAutoRefresh()` is called. With no interval set, only the initial
+	/// computation runs and later updates must be triggered manually via
+	/// `update()`.
+	func startAutoRefresh() {
+		stopAutoRefresh()
+
+		guard let interval = refresh, interval > 0 else {
+			// No interval: compute once, rely on manual updates afterwards.
+			Task { await update() }
+			return
+		}
+
+		let milliseconds = Int(interval * 1000)
+		refreshTask = Task { [weak self] in
+			while !Task.isCancelled {
+				await self?.update()
+				try? await Task.sleep(for: .milliseconds(milliseconds))
+			}
+		}
+	}
+
+	/// Cancel the repeating auto-refresh, if any.
+	func stopAutoRefresh() {
+		refreshTask?.cancel()
+		refreshTask = nil
+	}
+
+	/// Recompute the label from `command`. Used by auto-refresh and manual updates.
+	func update() async {
+		label = await compute()
+	}
+
+	/// Runs the provided command and returns its stdout.
+	///
+	/// Runs off the main actor so it can be awaited safely from SwiftUI views
+	/// without blocking the UI.
+	///
+	/// - Returns: A non-optional String to use as the block label.
+	func compute() async -> String {
+		let command = command
+		return await Task.detached(priority: .userInitiated) {
+			let process = Process()
+			process.executableURL = URL(fileURLWithPath: "/bin/bash")
+			process.arguments = ["-c", command]
+
+			// Inherit the parent's environment (includes $PATH, etc.)
+			process.environment = ProcessInfo.processInfo.environment
+
+			// Capture stdout via a pipe (otherwise standardOutput is always nil).
+			let pipe = Pipe()
+			process.standardOutput = pipe
+
+			do {
+				try process.run()
+				process.waitUntilExit()
+				let data = pipe.fileHandleForReading.readDataToEndOfFile()
+				return String(data: data, encoding: .utf8) ?? ""
+			} catch {
+				// Silently ignore failures
+				return ""
+			}
+		}.value
+	}
+}
+
+// Loading
+
+extension PHBlock {
+	private struct Wrapper: Decodable {
+		let blocks: [PHBlock]
+
+		enum CodingKeys: String, CodingKey {
+			case blocks = "block"
+		}
+	}
+
+	/// Load blocks from the default path (~/.config/phbar/blocks.toml).
+	/// If the file doesn't exist or fails to parse, defaults are used (non-fatal).
+	static func load() throws -> [PHBlock] {
+		let url = FileManager.default.homeDirectoryForCurrentUser.appending(
+			path: ".config/phbar/blocks.toml"
+		)
+
+		if FileManager.default.fileExists(atPath: url.relativePath) {
+			return try load(from: url)
+		} else {
+			throw phbar.Error("Failed to load blocks file")
+		}
+	}
+
+	/// Load theme from a file at URL.
+	/// If the file doesn't exist or fails to parse, the execution is interrupted.
+	static func load(from url: URL) throws -> [PHBlock] {
+		do {
+			let data = try Data(contentsOf: url)
+			guard let contents = String(data: data, encoding: .utf8), !contents.isEmpty else {
+				throw phbar.Error("the file is empty")
+			}
+			return try load(from: contents)
+		} catch {
+			throw phbar.Error("Failed to load blocks file", underlyingError: error)
+		}
+	}
+
+	/// Load theme from a TOML string.
+	/// If the content fails to parse, the execution is interrupted.
+	static func load(from contents: String) throws -> [PHBlock] {
+		do {
+			let decoder = TOMLDecoder()
+			let wrapper = try decoder.decode(PHBlock.Wrapper.self, from: contents)
+			return wrapper.blocks
+		} catch {
+			throw phbar.Error("Failed to parse blocks file", underlyingError: error)
+		}
+	}
+}
diff --git a/Sources/phbar/Views/BarView.swift b/Sources/phbar/Views/BarView.swift
new file mode 100644
index 0000000..8aa4aa6
--- /dev/null
+++ b/Sources/phbar/Views/BarView.swift
@@ -0,0 +1,23 @@
+import SwiftUI
+
+struct BarView: View {
+	@StateObject private var bar: PHController
+
+	init(controller: PHController) {
+		self._bar = StateObject(wrappedValue: controller)
+	}
+
+	var body: some View {
+		HStack(alignment: .center, spacing: 0) {
+			ForEach(bar.blocks) { block in
+				TextBlock(block: block)
+			}
+
+			SpaceBlock()
+		}
+		.font(.custom("Comic Code", size: 14))
+		.frame(height: 30)
+		.ignoresSafeArea()
+		.environmentObject(bar)
+	}
+}
diff --git a/Sources/phbar/Views/BarWindow.swift b/Sources/phbar/Views/BarWindow.swift
new file mode 100644
index 0000000..71a3108
--- /dev/null
+++ b/Sources/phbar/Views/BarWindow.swift
@@ -0,0 +1,54 @@
+import AppKit
+import SwiftUI
+
+final class BarWindow: NSPanel {
+	let barController: PHController
+	var barView: NSHostingView<BarView>!
+
+	init(controller: PHController) {
+		self.barController = controller
+
+		super.init(
+			contentRect: Self.computeFrame(from: barController),
+			styleMask: [.borderless, .nonactivatingPanel],
+			backing: .buffered,
+			defer: false
+		)
+
+		// self.delegate = self
+		self.title = "PMenu"
+		self.isFloatingPanel = true
+		self.level = .floating
+		self.animationBehavior = .utilityWindow
+		self.isOpaque = false
+		self.backgroundColor = .clear
+		// self.hasShadow = pmenu.config.window.shadow
+		self.collectionBehavior = [.canJoinAllSpaces, .fullScreenAuxiliary, .stationary]
+		self.acceptsMouseMovedEvents = false
+		self.isMovable = false
+		self.ignoresMouseEvents = false
+		self.hidesOnDeactivate = false
+		self.titleVisibility = .hidden
+		self.titlebarAppearsTransparent = true
+		self.isRestorable = false
+		self.displaysWhenScreenProfileChanges = true
+
+		self.barView = NSHostingView(rootView: BarView(controller: barController))
+		barView.autoresizingMask = [.width, .height]
+		barView.frame = self.contentView?.bounds ?? .zero
+
+		self.contentView = barView
+	}
+}
+
+extension BarWindow {
+	/// Calculate window frame and position.
+	static func computeFrame(from controller: PHController) -> NSRect {
+		let screenFrame = controller.screen.frame
+		let height: CGFloat = 30
+		let x = screenFrame.minX
+		let y = screenFrame.maxY - height
+
+		return NSRect(x: x, y: y, width: screenFrame.width, height: height)
+	}
+}
diff --git a/Sources/phbar/Views/Blocks/SpaceBlock.swift b/Sources/phbar/Views/Blocks/SpaceBlock.swift
new file mode 100644
index 0000000..08f656d
--- /dev/null
+++ b/Sources/phbar/Views/Blocks/SpaceBlock.swift
@@ -0,0 +1,8 @@
+import SwiftUI
+
+struct SpaceBlock: View {
+	var body: some View {
+		Rectangle()
+			.fill(.blue)
+	}
+}
diff --git a/Sources/phbar/Views/Blocks/TextBlock.swift b/Sources/phbar/Views/Blocks/TextBlock.swift
new file mode 100644
index 0000000..639303b
--- /dev/null
+++ b/Sources/phbar/Views/Blocks/TextBlock.swift
@@ -0,0 +1,16 @@
+import SwiftUI
+
+struct TextBlock: View {
+	@ObservedObject var block: PHBlock
+
+	var body: some View {
+		ZStack {
+			Rectangle()
+				.fill(.red)
+
+			Text(block.label)
+				.foregroundColor(.white)
+		}
+		.fixedSize(horizontal: true, vertical: false)
+	}
+}
diff --git a/Sources/phbar/cli.swift b/Sources/phbar/cli.swift
new file mode 100644
index 0000000..bca59d1
--- /dev/null
+++ b/Sources/phbar/cli.swift
@@ -0,0 +1,62 @@
+// The Swift Programming Language
+// https://docs.swift.org/swift-book
+//
+// Swift Argument Parser
+// https://swiftpackageindex.com/apple/swift-argument-parser/documentation
+
+import ArgumentParser
+import Foundation
+
+@main
+struct phbar: ParsableCommand {
+	static let configuration = CommandConfiguration(
+		commandName: "phbar",
+		abstract: "Modular status bar for macOS.",
+		discussion: """
+			pmenu reads a list of newline-separated items from stdin and presents them to the user.
+			When the user selects an item and presses Return, their choice is printed to stdout and pmenu terminates.
+			Entering text will narrow the items to those matching the tokens in the input.
+			""",
+		version: "1.0.0",
+		subcommands: [start.self]
+	)
+}
+
+extension phbar {
+	struct Error: LocalizedError {
+		let message: String
+		let underlyingError: Swift.Error?
+
+		init(_ message: String, underlyingError: Swift.Error? = nil) {
+			self.message = message
+			self.underlyingError = underlyingError
+		}
+
+		var errorDescription: String? {
+			guard let underlyingError else { return message }
+
+			if let decodingError = underlyingError as? DecodingError {
+				return "\(message): \(Self.describe(decodingError))"
+			}
+			return "\(message): \(underlyingError.localizedDescription)"
+		}
+
+		private static func describe(_ error: DecodingError) -> String {
+			switch error {
+			case .keyNotFound(let key, let context):
+				let path = context.codingPath.map(\.stringValue).joined(separator: ".")
+				return "missing key '\(key.stringValue)' at \(path.isEmpty ? "root" : path)"
+			case .typeMismatch(let type, let context):
+				let path = context.codingPath.map(\.stringValue).joined(separator: ".")
+				return "type mismatch for \(type) at \(path)"
+			case .valueNotFound(let type, let context):
+				let path = context.codingPath.map(\.stringValue).joined(separator: ".")
+				return "missing value of type \(type) at \(path)"
+			case .dataCorrupted(let context):
+				return "corrupted data → \(context.debugDescription)"
+			@unknown default:
+				return error.localizedDescription
+			}
+		}
+	}
+}
diff --git a/Sources/phbar/phbar.swift b/Sources/phbar/phbar.swift
deleted file mode 100644
index e7ed9be..0000000
--- a/Sources/phbar/phbar.swift
+++ /dev/null
@@ -1,14 +0,0 @@
-// The Swift Programming Language
-// https://docs.swift.org/swift-book
-//
-// Swift Argument Parser
-// https://swiftpackageindex.com/apple/swift-argument-parser/documentation
-
-import ArgumentParser
-
-@main
-struct phbar: ParsableCommand {
-	mutating func run() throws {
-		print("Hello, world!")
-	}
-}