diff --git a/archive/number-state-input.tsx b/archive/number-state-input.tsx
new file mode 100644
index 0000000..2da20e8
--- /dev/null
+++ b/archive/number-state-input.tsx
@@ -0,0 +1,32 @@
+interface StateInputProps<T> {
+    state: PrimitiveAtom<T>;
+    className?: string;
+}
+
+const NumberStateInput: FC<StateInputProps<number | null>> = (
+    props: StateInputProps<number | null>
+) => {
+    const { state, className } = props;
+    const [number, setNumber] = useAtom(state);
+
+    const handleChange = useCallback(
+        (e: ChangeEvent<HTMLInputElement>) => {
+            const re = /^\d*$/;
+            const v = e.target.value;
+            if (v === '') {
+                setNumber(null);
+            } else if (re.test(v)) {
+                setNumber(parseInt(v));
+            }
+        },
+        [setNumber]
+    );
+
+    return (
+        <input
+            className={className}
+            value={number ?? ''}
+            onChange={handleChange}
+        />
+    );
+};
diff --git a/src/atoms.ts b/src/atoms.ts
index e727f00..9775cb2 100644
--- a/src/atoms.ts
+++ b/src/atoms.ts
@@ -16,6 +16,3 @@ type DrawMode = 'line' | 'trash' | 'grid';
 export const lineColorState = atom<string>(COLORS[0]!);
 
 export const drawModeState = atom<DrawMode>('line');
-
-export const drawGridWidthState = atom<number | null>(4);
-export const drawGridHeightState = atom<number | null>(4);
diff --git a/src/components/grid/grid-config.tsx b/src/components/grid/grid-config.tsx
index 5791120..3b3c6b9 100644
--- a/src/components/grid/grid-config.tsx
+++ b/src/components/grid/grid-config.tsx
@@ -1,12 +1,6 @@
 import { ChangeEvent, FC, useCallback } from 'react';
-import { PrimitiveAtom, useAtom, WritableAtom } from 'jotai';
-import {
-    COLORS,
-    drawGridHeightState,
-    drawGridWidthState,
-    drawModeState,
-    lineColorState,
-} from '../../atoms';
+import { PrimitiveAtom, useAtom } from 'jotai';
+import { COLORS, drawModeState, lineColorState } from '../../atoms';
 
 import './grid-config.scss';
 
@@ -46,16 +40,14 @@ const GridIcon = (
     <svg
         className="icon"
         xmlns="http://www.w3.org/2000/svg"
-        width="12"
-        height="12"
-        viewBox="0 0 12 12"
+        viewBox="0 0 24 13"
     >
-        <line x1="0" y1="0" x2="12" y2="0" stroke="#ffffff" strokeWidth="2" />
-        <line x1="0" y1="6" x2="12" y2="6" stroke="#ffffff" strokeWidth="2" />
-        <line x1="0" y1="12" x2="12" y2="12" stroke="#ffffff" strokeWidth="2" />
-        <line x1="0" y1="0" x2="0" y2="12" stroke="#ffffff" strokeWidth="2" />
-        <line x1="6" y1="0" x2="6" y2="12" stroke="#ffffff" strokeWidth="2" />
-        <line x1="12" y1="0" x2="12" y2="12" stroke="#ffffff" strokeWidth="2" />
+        <line x1="5" y1="0" x2="18" y2="0" stroke="#ffffff" strokeWidth="4" />
+        <line x1="5" y1="7" x2="18" y2="7" stroke="#ffffff" strokeWidth="2" />
+        <line x1="5" y1="13" x2="18" y2="13" stroke="#ffffff" strokeWidth="4" />
+        <line x1="5" y1="0" x2="5" y2="13" stroke="#ffffff" strokeWidth="2" />
+        <line x1="11" y1="0" x2="11" y2="13" stroke="#ffffff" strokeWidth="2" />
+        <line x1="17" y1="0" x2="17" y2="13" stroke="#ffffff" strokeWidth="2" />
     </svg>
 );
 
@@ -84,39 +76,6 @@ const ColorOption: FC<ColorOptionProps> = (props: ColorOptionProps) => {
     );
 };
 
-interface StateInputProps<T> {
-    state: PrimitiveAtom<T>;
-    className?: string;
-}
-
-const NumberStateInput: FC<StateInputProps<number | null>> = (
-    props: StateInputProps<number | null>
-) => {
-    const { state, className } = props;
-    const [number, setNumber] = useAtom(state);
-
-    const handleChange = useCallback(
-        (e: ChangeEvent<HTMLInputElement>) => {
-            const re = /^\d*$/;
-            const v = e.target.value;
-            if (v === '') {
-                setNumber(null);
-            } else if (re.test(v)) {
-                setNumber(parseInt(v));
-            }
-        },
-        [setNumber]
-    );
-
-    return (
-        <input
-            className={className}
-            value={number ?? ''}
-            onChange={handleChange}
-        />
-    );
-};
-
 const ColorConfig: FC = () => (
     <div className="color-options">
         {COLORS.map((color) => (
@@ -130,8 +89,7 @@ const ModeConfig: FC = () => {
 
     const lineClassName = drawMode === 'line' ? 'option active' : 'option';
     const trashClassName = drawMode === 'trash' ? 'option active' : 'option';
-    const gridClassName =
-        drawMode === 'grid' ? 'option active grid' : 'option grid';
+    const gridClassName = drawMode === 'grid' ? 'option active' : 'option';
     return (
         <>
             <div className="tool-options">
@@ -147,22 +105,11 @@ const ModeConfig: FC = () => {
                 >
                     {TrashIcon}
                 </div>
-            </div>
-            <div className="grid-options">
                 <div
                     className={gridClassName}
                     onClick={() => setDrawMode('grid')}
                 >
                     {GridIcon}
-                    <NumberStateInput
-                        className="grid-size width"
-                        state={drawGridWidthState}
-                    />
-                    <span className="x">x</span>
-                    <NumberStateInput
-                        className="grid-size height"
-                        state={drawGridHeightState}
-                    />
                 </div>
             </div>
         </>
diff --git a/src/components/grid/grid.tsx b/src/components/grid/grid.tsx
index 97d67a0..df5e1ff 100644
--- a/src/components/grid/grid.tsx
+++ b/src/components/grid/grid.tsx
@@ -181,7 +181,14 @@ const Grid: FC = () => {
                 return;
             }
 
-            const point = snapToGrid(mousePoint, GAP);
+            let point;
+            if (userDrawMode === 'grid') {
+                // snap to the thick grid
+                point = snapToGrid(mousePoint, GAP * 6);
+            } else {
+                // snap to the thin grid for line / trash
+                point = snapToGrid(mousePoint, GAP);
+            }
 
             if (lodash.isEqual(userStartPoint, point)) {
                 setUserStartPoint(null);
@@ -249,6 +256,12 @@ const Grid: FC = () => {
 
     // ctrl+z/ctrl+y for undo/redo
     const onUndo = useCallback(() => {
+        if (!lodash.isNull(userStartPoint)) {
+            // if the user has a start point, just cancel the pending line
+            setUserStartPoint(null);
+            return;
+        }
+
         const action = userActions[userActions.length - 1];
         if (!action) return;
 
@@ -264,7 +277,7 @@ const Grid: FC = () => {
         }
         setUserActions(userActions.slice(0, -1));
         setUserRedoActions([...userRedoActions, action]);
-    }, [userLines, userActions, userRedoActions]);
+    }, [userLines, userActions, userRedoActions, userStartPoint]);
 
     const onRedo = useCallback(() => {
         const action = userRedoActions[userRedoActions.length - 1];
@@ -341,6 +354,7 @@ const Grid: FC = () => {
                     strokeWidth="2"
                 />
             );
+            // TODO: grid mode
         } else {
             console.assert(userDrawMode === 'trash');
             return (