diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0e0763e..a27c1c4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
  * Add ability to export to Markdown (and fix heading styles)
  * Represent in the History diff pane when an image was the thing that changed
  * Support theme choice in settings (light/dark/system)
+ * Add Checkboxes in the editor. Typing 'TODO' at the start of a line will auto-convert into a checkbox.
 
 # 0.1.9
 
diff --git a/bouquin/editor.py b/bouquin/editor.py
index f68d3c1..05ef128 100644
--- a/bouquin/editor.py
+++ b/bouquin/editor.py
@@ -45,6 +45,11 @@ class Editor(QTextEdit):
     _HEADING_SIZES = (24.0, 18.0, 14.0)
     _IMAGE_EXTS = (".png", ".jpg", ".jpeg", ".bmp", ".gif", ".webp")
     _DATA_IMG_RX = re.compile(r'src=["\']data:image/[^;]+;base64,([^"\']+)["\']', re.I)
+    # --- Checkbox hack --- #
+    _CHECK_UNCHECKED = "\u2610"  # ☐
+    _CHECK_CHECKED = "\u2611"  # ☑
+    _CHECK_RX = re.compile(r"^\s*([\u2610\u2611])\s")  # ☐/☑ plus a space
+    _CHECKBOX_SCALE = 1.35
 
     def __init__(self, theme_manager: ThemeManager, *args, **kwargs):
         super().__init__(*args, **kwargs)
@@ -451,11 +456,52 @@ class Editor(QTextEdit):
             self.viewport().setCursor(Qt.IBeamCursor)
         super().mouseMoveEvent(e)
 
+    def mousePressEvent(self, e):
+        if e.button() == Qt.LeftButton and not (e.modifiers() & Qt.ControlModifier):
+            cur = self.cursorForPosition(e.pos())
+            b = cur.block()
+            state, pref = self._checkbox_info_for_block(b)
+            if state is not None:
+                col = cur.position() - b.position()
+                if col <= max(1, pref):  # clicked on ☐/☑ (and the following space)
+                    self._set_block_checkbox_state(b, not state)
+                    return
+        return super().mousePressEvent(e)
+
     def keyPressEvent(self, e):
         key = e.key()
 
-        # Pre-insert: stop link/format bleed for “word boundary” keys
         if key in (Qt.Key_Space, Qt.Key_Tab):
+            c = self.textCursor()
+            b = c.block()
+            pos_in_block = c.position() - b.position()
+
+            if (
+                pos_in_block >= 4
+                and b.text().startswith("TODO")
+                and b.text()[:pos_in_block] == "TODO"
+                and self._checkbox_info_for_block(b)[0] is None
+            ):
+                tcur = QTextCursor(self.document())
+                tcur.setPosition(b.position())  # start of block
+                tcur.setPosition(
+                    b.position() + 4, QTextCursor.KeepAnchor
+                )  # select "TODO"
+                tcur.beginEditBlock()
+                tcur.removeSelectedText()
+                tcur.insertText(self._CHECK_UNCHECKED + " ")  # insert "☐ "
+                tcur.endEditBlock()
+
+                # visuals: size bump
+                if hasattr(self, "_style_checkbox_glyph"):
+                    self._style_checkbox_glyph(b)
+
+                # caret after the inserted prefix; swallow the key (we already added a space)
+                c.setPosition(b.position() + 2)
+                self.setTextCursor(c)
+                return
+
+            # not a TODO-at-start case
             self._break_anchor_for_next_char()
             return super().keyPressEvent(e)
 
@@ -472,6 +518,26 @@ class Editor(QTextEdit):
                     super().insertPlainText("\n")  # start a normal paragraph
                     return
 
+            # --- CHECKBOX handling: continue on Enter; "escape" on second Enter ---
+            b = c.block()
+            state, pref = self._checkbox_info_for_block(b)
+            if state is not None and not c.hasSelection():
+                text_after = b.text()[pref:].strip()
+                if c.atBlockEnd() and text_after == "":
+                    # Empty checkbox item -> remove the prefix and insert a plain new line
+                    cur = QTextCursor(self.document())
+                    cur.setPosition(b.position())
+                    cur.movePosition(QTextCursor.Right, QTextCursor.KeepAnchor, pref)
+                    cur.removeSelectedText()
+                    return super().keyPressEvent(e)
+                else:
+                    # Normal continuation: new checkbox on the next line
+                    super().keyPressEvent(e)  # make the new block
+                    super().insertPlainText(self._CHECK_UNCHECKED + " ")
+                    if hasattr(self, "_style_checkbox_glyph"):
+                        self._style_checkbox_glyph(self.textCursor().block())
+                    return
+
             # Follow-on style: if we typed a heading and press Enter at end of block,
             # new paragraph should revert to Normal.
             if not c.hasSelection() and c.atBlockEnd() and self._is_heading_typing():
@@ -520,6 +586,125 @@ class Editor(QTextEdit):
             cursor.mergeCharFormat(fmt)
         self.mergeCurrentCharFormat(fmt)
 
+    # ====== Checkbox core ======
+    def _base_point_size_for_block(self, block) -> float:
+        # Try the block’s char format, then editor font
+        sz = block.charFormat().fontPointSize()
+        if sz <= 0:
+            sz = self.fontPointSize()
+        if sz <= 0:
+            sz = self.font().pointSizeF() or 12.0
+        return float(sz)
+
+    def _style_checkbox_glyph(self, block):
+        """Apply larger size (and optional symbol font) to the single ☐/☑ char."""
+        state, _ = self._checkbox_info_for_block(block)
+        if state is None:
+            return
+        doc = self.document()
+        c = QTextCursor(doc)
+        c.setPosition(block.position())
+        c.movePosition(QTextCursor.Right, QTextCursor.KeepAnchor, 1)  # select ☐/☑ only
+
+        base = self._base_point_size_for_block(block)
+        fmt = QTextCharFormat()
+        fmt.setFontPointSize(base * self._CHECKBOX_SCALE)
+        # keep the glyph centered on the text baseline
+        fmt.setVerticalAlignment(QTextCharFormat.AlignMiddle)
+
+        c.mergeCharFormat(fmt)
+
+    def _checkbox_info_for_block(self, block):
+        """Return (state, prefix_len): state in {None, False, True}, prefix_len in chars."""
+        text = block.text()
+        m = self._CHECK_RX.match(text)
+        if not m:
+            return None, 0
+        ch = m.group(1)
+        state = True if ch == self._CHECK_CHECKED else False
+        return state, m.end()
+
+    def _set_block_checkbox_present(self, block, present: bool):
+        state, pref = self._checkbox_info_for_block(block)
+        doc = self.document()
+        c = QTextCursor(doc)
+        c.setPosition(block.position())
+        c.beginEditBlock()
+        try:
+            if present and state is None:
+                c.insertText(self._CHECK_UNCHECKED + " ")
+                state = False
+                self._style_checkbox_glyph(block)
+            else:
+                if state is not None:
+                    c.movePosition(QTextCursor.Right, QTextCursor.KeepAnchor, pref)
+                    c.removeSelectedText()
+                    state = None
+        finally:
+            c.endEditBlock()
+
+        return state
+
+    def _set_block_checkbox_state(self, block, checked: bool):
+        """Switch ☐/☑ at the start of the block."""
+        state, pref = self._checkbox_info_for_block(block)
+        if state is None:
+            return
+        doc = self.document()
+        c = QTextCursor(doc)
+        c.setPosition(block.position())
+        c.movePosition(QTextCursor.Right, QTextCursor.KeepAnchor, 1)  # just the symbol
+        c.beginEditBlock()
+        try:
+            c.removeSelectedText()
+            c.insertText(self._CHECK_CHECKED if checked else self._CHECK_UNCHECKED)
+            self._style_checkbox_glyph(block)
+        finally:
+            c.endEditBlock()
+
+    # Public API used by toolbar
+    def toggle_checkboxes(self):
+        """
+        Toggle checkbox prefix on/off for the current block(s).
+        If all targeted blocks already have a checkbox, remove them; otherwise add.
+        """
+        c = self.textCursor()
+        doc = self.document()
+
+        if c.hasSelection():
+            start = doc.findBlock(c.selectionStart())
+            end = doc.findBlock(c.selectionEnd() - 1)
+        else:
+            start = end = c.block()
+
+        # Decide intent: add or remove?
+        b = start
+        all_have = True
+        while True:
+            state, _ = self._checkbox_info_for_block(b)
+            if state is None:
+                all_have = False
+                break
+            if b == end:
+                break
+            b = b.next()
+
+        # Apply
+        b = start
+        while True:
+            self._set_block_checkbox_present(b, present=not all_have)
+            if b == end:
+                break
+            b = b.next()
+
+    def toggle_current_checkbox_state(self):
+        """Tick/untick the current line if it starts with a checkbox."""
+        b = self.textCursor().block()
+        state, _ = self._checkbox_info_for_block(b)
+        if state is None:
+            return
+        self._set_block_checkbox_state(b, not state)
+
     @Slot()
     def apply_weight(self):
         cur = self.currentCharFormat()
diff --git a/bouquin/lock_overlay.py b/bouquin/lock_overlay.py
new file mode 100644
index 0000000..d019f3b
--- /dev/null
+++ b/bouquin/lock_overlay.py
@@ -0,0 +1,127 @@
+from __future__ import annotations
+
+from PySide6.QtCore import Qt, QEvent
+from PySide6.QtGui import QPalette
+from PySide6.QtWidgets import QWidget, QVBoxLayout, QLabel, QPushButton
+
+
+class LockOverlay(QWidget):
+    def __init__(self, parent: QWidget, on_unlock: callable):
+        super().__init__(parent)
+        self.setObjectName("LockOverlay")
+        self.setAttribute(Qt.WA_StyledBackground, True)
+        self.setFocusPolicy(Qt.StrongFocus)
+        self.setGeometry(parent.rect())
+
+        self._styling = False  # <-- reentrancy guard
+        self._last_dark: bool | None = None
+
+        lay = QVBoxLayout(self)
+        lay.addStretch(1)
+
+        msg = QLabel("Locked due to inactivity", self)
+        msg.setObjectName("lockLabel")
+        msg.setAlignment(Qt.AlignCenter)
+
+        self._btn = QPushButton("Unlock", self)
+        self._btn.setObjectName("unlockButton")
+        self._btn.setFixedWidth(200)
+        self._btn.setCursor(Qt.PointingHandCursor)
+        self._btn.setAutoDefault(True)
+        self._btn.setDefault(True)
+        self._btn.clicked.connect(on_unlock)
+
+        lay.addWidget(msg, 0, Qt.AlignCenter)
+        lay.addWidget(self._btn, 0, Qt.AlignCenter)
+        lay.addStretch(1)
+
+        self._apply_overlay_style()
+        self.hide()
+
+    def _is_dark(self, pal: QPalette) -> bool:
+        c = pal.color(QPalette.Window)
+        luma = 0.2126 * c.redF() + 0.7152 * c.greenF() + 0.0722 * c.blueF()
+        return luma < 0.5
+
+    def _apply_overlay_style(self):
+        if self._styling:
+            return
+        dark = self._is_dark(self.palette())
+        if dark == self._last_dark:
+            return
+        self._styling = True
+        try:
+            if dark:
+                link = self.palette().color(QPalette.Link)
+                accent_hex = link.name()  # e.g. "#FFA500"
+                r, g, b = link.red(), link.green(), link.blue()
+
+                self.setStyleSheet(
+                    f"""
+#LockOverlay {{ background-color: rgb(0,0,0); }}   /* opaque, no transparency */
+#LockOverlay QLabel#lockLabel {{ color: {accent_hex}; font-weight: 600; }}
+
+#LockOverlay QPushButton#unlockButton {{
+    color: {accent_hex};
+    background-color: rgba({r},{g},{b},0.10);
+    border: 1px solid {accent_hex};
+    border-radius: 8px;
+    padding: 8px 16px;
+}}
+#LockOverlay QPushButton#unlockButton:hover {{
+    background-color: rgba({r},{g},{b},0.16);
+    border-color: {accent_hex};
+}}
+#LockOverlay QPushButton#unlockButton:pressed {{
+    background-color: rgba({r},{g},{b},0.24);
+}}
+#LockOverlay QPushButton#unlockButton:focus {{
+    outline: none;
+    border-color: {accent_hex};
+}}
+    """
+                )
+            else:
+                # (light mode unchanged)
+                self.setStyleSheet(
+                    """
+#LockOverlay { background-color: rgba(0,0,0,120); }
+#LockOverlay QLabel#lockLabel { color: palette(window-text); font-weight: 600; }
+#LockOverlay QPushButton#unlockButton {
+    color: palette(button-text);
+    background-color: rgba(255,255,255,0.92);
+    border: 1px solid rgba(0,0,0,0.25);
+    border-radius: 8px;
+    padding: 8px 16px;
+}
+#LockOverlay QPushButton#unlockButton:hover {
+    background-color: rgba(255,255,255,1.0);
+    border-color: rgba(0,0,0,0.35);
+}
+#LockOverlay QPushButton#unlockButton:pressed {
+    background-color: rgba(245,245,245,1.0);
+}
+#LockOverlay QPushButton#unlockButton:focus {
+    outline: none;
+    border-color: palette(highlight);
+}
+    """
+                )
+            self._last_dark = dark
+        finally:
+            self._styling = False
+
+    def changeEvent(self, ev):
+        super().changeEvent(ev)
+        # Only re-style on palette flips
+        if ev.type() in (QEvent.PaletteChange, QEvent.ApplicationPaletteChange):
+            self._apply_overlay_style()
+
+    def eventFilter(self, obj, event):
+        if obj is self.parent() and event.type() in (QEvent.Resize, QEvent.Show):
+            self.setGeometry(obj.rect())
+        return False
+
+    def showEvent(self, e):
+        super().showEvent(e)
+        self._btn.setFocus()
diff --git a/bouquin/main_window.py b/bouquin/main_window.py
index 7b29bbc..7c9d1d0 100644
--- a/bouquin/main_window.py
+++ b/bouquin/main_window.py
@@ -32,10 +32,8 @@ from PySide6.QtWidgets import (
     QCalendarWidget,
     QDialog,
     QFileDialog,
-    QLabel,
     QMainWindow,
     QMessageBox,
-    QPushButton,
     QSizePolicy,
     QSplitter,
     QVBoxLayout,
@@ -46,6 +44,7 @@ from .db import DBManager
 from .editor import Editor
 from .history_dialog import HistoryDialog
 from .key_prompt import KeyPrompt
+from .lock_overlay import LockOverlay
 from .save_dialog import SaveDialog
 from .search import Search
 from .settings import APP_ORG, APP_NAME, load_db_config, save_db_config
@@ -54,78 +53,6 @@ from .toolbar import ToolBar
 from .theme import Theme, ThemeManager
 
 
-class _LockOverlay(QWidget):
-    def __init__(self, parent: QWidget, on_unlock: callable):
-        super().__init__(parent)
-        self.setObjectName("LockOverlay")
-        self.setAttribute(Qt.WA_StyledBackground, True)
-        self.setFocusPolicy(Qt.StrongFocus)
-        self.setGeometry(parent.rect())
-
-        lay = QVBoxLayout(self)
-        lay.addStretch(1)
-
-        msg = QLabel("Locked due to inactivity")
-        msg.setAlignment(Qt.AlignCenter)
-
-        self._btn = QPushButton("Unlock")
-        self._btn.setFixedWidth(200)
-        self._btn.setCursor(Qt.PointingHandCursor)
-        self._btn.setAutoDefault(True)
-        self._btn.setDefault(True)
-        self._btn.clicked.connect(on_unlock)
-
-        lay.addWidget(msg, 0, Qt.AlignCenter)
-        lay.addWidget(self._btn, 0, Qt.AlignCenter)
-        lay.addStretch(1)
-
-        self._apply_overlay_style()
-
-        self.hide()  # start hidden
-
-    def _apply_overlay_style(self):
-        pal = self.palette()
-        bg = (
-            pal.window().color().darker(180)
-            if pal.color(QPalette.Window).value() < 128
-            else pal.window().color().lighter(110)
-        )
-        text = pal.windowText().color()
-        btn_bg = pal.button().color()
-        btn_fg = pal.buttonText().color()
-        border = pal.mid().color()
-
-        hover_bg = btn_bg.lighter(106)  # +6%
-        press_bg = btn_bg.darker(106)  # -6%
-
-        self.setStyleSheet(
-            f"""
-    #LockOverlay {{ background-color: {bg.name()}; }}
-    #LockOverlay QLabel {{ color: {text.name()}; font-size: 18px; }}
-    #LockOverlay QPushButton {{
-        background-color: {btn_bg.name()};
-        color: {btn_fg.name()};
-        padding: 6px 14px;
-        border: 1px solid {border.name()};
-        border-radius: 6px;
-        font-size: 14px;
-    }}
-    #LockOverlay QPushButton:hover   {{ background-color: {hover_bg.name()}; }}
-    #LockOverlay QPushButton:pressed {{ background-color: {press_bg.name()}; }}
-    """
-        )
-
-    # keep overlay sized with its parent
-    def eventFilter(self, obj, event):
-        if obj is self.parent() and event.type() in (QEvent.Resize, QEvent.Show):
-            self.setGeometry(obj.rect())
-        return False
-
-    def showEvent(self, e):
-        super().showEvent(e)
-        self._btn.setFocus()
-
-
 class MainWindow(QMainWindow):
     def __init__(self, themes: ThemeManager, *args, **kwargs):
         super().__init__(*args, **kwargs)
@@ -182,6 +109,7 @@ class MainWindow(QMainWindow):
         self.toolBar.headingRequested.connect(self.editor.apply_heading)
         self.toolBar.bulletsRequested.connect(self.editor.toggle_bullets)
         self.toolBar.numbersRequested.connect(self.editor.toggle_numbers)
+        self.toolBar.checkboxesRequested.connect(self.editor.toggle_checkboxes)
         self.toolBar.alignRequested.connect(self.editor.setAlignment)
         self.toolBar.historyRequested.connect(self._open_history)
         self.toolBar.insertImageRequested.connect(self._on_insert_image)
@@ -207,8 +135,7 @@ class MainWindow(QMainWindow):
         self._idle_timer.start()
 
         # full-window overlay that sits on top of the central widget
-        self._lock_overlay = _LockOverlay(self.centralWidget(), self._on_unlock_clicked)
-        self._lock_overlay._apply_overlay_style()
+        self._lock_overlay = LockOverlay(self.centralWidget(), self._on_unlock_clicked)
         self.centralWidget().installEventFilter(self._lock_overlay)
 
         self._locked = False
@@ -375,7 +302,6 @@ class MainWindow(QMainWindow):
             pass
 
         try:
-            # Apply to the search widget (if it's also a rich-text widget)
             self.search.document().setDefaultStyleSheet(css)
         except Exception:
             pass
@@ -562,7 +488,7 @@ class MainWindow(QMainWindow):
 
     def _on_text_changed(self):
         self._dirty = True
-        self._save_timer.start(10000)  # autosave after idle
+        self._save_timer.start(5000)  # autosave after idle
 
     def _adjust_day(self, delta: int):
         """Move selection by delta days (negative for previous)."""
diff --git a/bouquin/toolbar.py b/bouquin/toolbar.py
index 5d5c451..78c737e 100644
--- a/bouquin/toolbar.py
+++ b/bouquin/toolbar.py
@@ -14,6 +14,7 @@ class ToolBar(QToolBar):
     headingRequested = Signal(int)
     bulletsRequested = Signal()
     numbersRequested = Signal()
+    checkboxesRequested = Signal()
     alignRequested = Signal(Qt.AlignmentFlag)
     historyRequested = Signal()
     insertImageRequested = Signal()
@@ -86,6 +87,9 @@ class ToolBar(QToolBar):
         self.actNumbers.setToolTip("Numbered list")
         self.actNumbers.setCheckable(True)
         self.actNumbers.triggered.connect(self.numbersRequested)
+        self.actCheckboxes = QAction("☐", self)
+        self.actCheckboxes.setToolTip("Toggle checkboxes")
+        self.actCheckboxes.triggered.connect(self.checkboxesRequested)
 
         # Images
         self.actInsertImg = QAction("Image", self)
@@ -150,6 +154,7 @@ class ToolBar(QToolBar):
                 self.actNormal,
                 self.actBullets,
                 self.actNumbers,
+                self.actCheckboxes,
                 self.actInsertImg,
                 self.actAlignL,
                 self.actAlignC,