diff --git a/src/avatar.tsx b/src/avatar.tsx
index dacc3b8..f4064c5 100644
--- a/src/avatar.tsx
+++ b/src/avatar.tsx
@@ -4,6 +4,7 @@ import "hono/jsx"
 import type { FC, JSX } from "hono/jsx"
 import { VStack, HStack } from "./stack"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 export type AvatarProps = {
   src: string
@@ -24,7 +25,7 @@ export const Avatar: FC<AvatarProps> = (props) => {
     ...style,
   }
 
-  return <img src={src} alt={alt} class={className} style={avatarStyle} />
+  return <img src={src} alt={alt} class={cn("Avatar", className)} style={avatarStyle} />
 }
 
 export const Test = () => {
diff --git a/src/box.tsx b/src/box.tsx
index f152a3f..68f444c 100644
--- a/src/box.tsx
+++ b/src/box.tsx
@@ -1,6 +1,7 @@
 import "hono/jsx"
 import type { FC, PropsWithChildren, JSX } from "hono/jsx"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 type BoxProps = PropsWithChildren & {
   bg?: string
@@ -18,7 +19,7 @@ export const Box: FC<BoxProps> = ({ children, bg, color, p, class: className, st
     ...style,
   }
 
-  return <div class={className} style={boxStyle}>{children}</div>
+  return <div class={cn("Box", className)} style={boxStyle}>{children}</div>
 }
 
 // Common demo box colors
diff --git a/src/button.tsx b/src/button.tsx
index b26161d..590d046 100644
--- a/src/button.tsx
+++ b/src/button.tsx
@@ -4,6 +4,7 @@ import { VStack, HStack } from "./stack"
 import { Section } from "./section"
 import { H2 } from "./text"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 export type ButtonProps = JSX.IntrinsicElements["button"] & {
   variant?: "primary" | "secondary" | "outline" | "ghost" | "destructive"
@@ -11,7 +12,7 @@ export type ButtonProps = JSX.IntrinsicElements["button"] & {
 }
 
 export const Button: FC<ButtonProps> = (props) => {
-  const { variant = "primary", size = "md", style, ...buttonProps } = props
+  const { variant = "primary", size = "md", style, class: className, ...buttonProps } = props
 
   const baseStyles: JSX.CSSProperties = {
     display: "inline-flex",
@@ -74,7 +75,7 @@ export const Button: FC<ButtonProps> = (props) => {
     ...(style as JSX.CSSProperties),
   }
 
-  return <button {...buttonProps} style={combinedStyles} />
+  return <button {...buttonProps} class={cn("Button", className)} style={combinedStyles} />
 }
 
 export const Test = () => {
diff --git a/src/cn.ts b/src/cn.ts
new file mode 100644
index 0000000..4db6805
--- /dev/null
+++ b/src/cn.ts
@@ -0,0 +1,11 @@
+/**
+ * Utility function to merge class names
+ * Filters out falsy values and joins remaining classes with spaces
+ *
+ * @example
+ * cn('base-class', isActive && 'active', 'another-class') // => "base-class active another-class"
+ * cn('foo', false, 'bar', null, undefined) // => "foo bar"
+ */
+export function cn(...classes: (string | undefined | null | false)[]): string {
+  return classes.filter(Boolean).join(" ");
+}
diff --git a/src/divider.tsx b/src/divider.tsx
index 6030215..48cb460 100644
--- a/src/divider.tsx
+++ b/src/divider.tsx
@@ -4,6 +4,7 @@ import "hono/jsx"
 import type { FC, PropsWithChildren, JSX } from "hono/jsx"
 import { VStack } from "./stack"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 type DividerProps = PropsWithChildren & {
   class?: string
@@ -31,7 +32,7 @@ export const Divider: FC<DividerProps> = ({ children, class: className, style })
   }
 
   return (
-    <div class={className} style={containerStyle}>
+    <div class={cn("Divider", className)} style={containerStyle}>
       <div style={lineStyle}></div>
       {children && (
         <>
diff --git a/src/grid.tsx b/src/grid.tsx
index 26039b1..ab064b2 100644
--- a/src/grid.tsx
+++ b/src/grid.tsx
@@ -6,6 +6,7 @@ import { Button } from "./button"
 import { Section } from "./section"
 import { H2, H3 } from "./text"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 type GridProps = PropsWithChildren & {
   cols?: GridCols
@@ -42,7 +43,7 @@ export const Grid: FC<GridProps> = (props) => {
     ...style,
   }
 
-  return <div class={className} style={combinedStyles}>{children}</div>
+  return <div class={cn("Grid", className)} style={combinedStyles}>{children}</div>
 }
 
 function getColumnsValue(cols: GridCols): string {
diff --git a/src/icon.tsx b/src/icon.tsx
index 8e411bc..bb9d3b4 100644
--- a/src/icon.tsx
+++ b/src/icon.tsx
@@ -6,6 +6,7 @@ import { VStack } from "./stack"
 import { Section } from "./section"
 import { H2, Text } from "./text"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 export type IconName = keyof typeof icons
 
@@ -46,7 +47,7 @@ export const Icon: FC<IconProps> = (props) => {
     .replace(/class="[^"]*"/, "")
     .replace(
       /<svg([^>]*)>/,
-      `<svg$1 style="display: block; flex-shrink: 0; width: ${pixelSize}px; height: ${pixelSize}px;" class="${className || ""}">`
+      `<svg$1 style="display: block; flex-shrink: 0; width: ${pixelSize}px; height: ${pixelSize}px;" class="${cn("Icon", className)}">`
     )
 
   return <div dangerouslySetInnerHTML={{ __html: modifiedSvg }} style={iconStyle} />
@@ -64,7 +65,7 @@ export const IconLink: FC<IconLinkProps> = (props) => {
   }
 
   return (
-    <a href={href} target={target} class={className} style={linkStyle}>
+    <a href={href} target={target} class={cn("IconLink", className)} style={linkStyle}>
       <Icon {...iconProps} />
     </a>
   )
diff --git a/src/image.tsx b/src/image.tsx
index 9a09dda..e3d2955 100644
--- a/src/image.tsx
+++ b/src/image.tsx
@@ -5,6 +5,7 @@ import type { FC, JSX } from "hono/jsx"
 import { VStack, HStack } from "./stack"
 import { Grid } from "./grid"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 export type ImageProps = {
   src: string
@@ -24,7 +25,7 @@ export const Image: FC<ImageProps> = ({ src, alt = "", width, height, objectFit,
     ...style,
   }
 
-  return <img src={src} alt={alt} class={className} style={imageStyle} />
+  return <img src={src} alt={alt} class={cn("Image", className)} style={imageStyle} />
 }
 
 export const Test = () => {
diff --git a/src/input.tsx b/src/input.tsx
index 089daf3..3234b39 100644
--- a/src/input.tsx
+++ b/src/input.tsx
@@ -4,6 +4,7 @@ import "hono/jsx"
 import type { JSX, FC } from "hono/jsx"
 import { VStack, HStack } from "./stack"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 export type InputProps = JSX.IntrinsicElements["input"] & {
   labelPosition?: "above" | "left" | "right"
@@ -11,7 +12,7 @@ export type InputProps = JSX.IntrinsicElements["input"] & {
 }
 
 export const Input: FC<InputProps> = (props) => {
-  const { labelPosition = "above", children, style, ...inputProps } = props
+  const { labelPosition = "above", children, style, class: className, ...inputProps } = props
 
   const inputStyle: JSX.CSSProperties = {
     height: "40px",
@@ -25,7 +26,7 @@ export const Input: FC<InputProps> = (props) => {
   }
 
   if (!children) {
-    return <input style={inputStyle} {...inputProps} />
+    return <input style={inputStyle} {...inputProps} class={cn("Input", className)} />
   }
 
   const labelStyle: JSX.CSSProperties = {
@@ -44,7 +45,7 @@ export const Input: FC<InputProps> = (props) => {
     return (
       <div style={{ display: "flex", flexDirection: "column", gap: "4px", flex: 1, minWidth: 0 }}>
         {labelElement}
-        <input style={inputStyle} {...inputProps} />
+        <input style={inputStyle} {...inputProps} class={cn("Input", className)} />
       </div>
     )
   }
@@ -53,7 +54,7 @@ export const Input: FC<InputProps> = (props) => {
     return (
       <div style={{ display: "flex", alignItems: "center", gap: "4px", flex: 1 }}>
         {labelElement}
-        <input style={{ ...inputStyle, flex: 1 }} {...inputProps} />
+        <input style={{ ...inputStyle, flex: 1 }} {...inputProps} class={cn("Input", className)} />
       </div>
     )
   }
@@ -61,7 +62,7 @@ export const Input: FC<InputProps> = (props) => {
   if (labelPosition === "right") {
     return (
       <div style={{ display: "flex", alignItems: "center", gap: "4px", flex: 1 }}>
-        <input style={{ ...inputStyle, flex: 1 }} {...inputProps} />
+        <input style={{ ...inputStyle, flex: 1 }} {...inputProps} class={cn("Input", className)} />
         {labelElement}
       </div>
     )
diff --git a/src/select.tsx b/src/select.tsx
index 3f6440e..e7606c0 100644
--- a/src/select.tsx
+++ b/src/select.tsx
@@ -4,6 +4,7 @@ import "hono/jsx"
 import type { JSX, FC } from "hono/jsx"
 import { VStack, HStack } from "./stack"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 export type SelectOption = {
   value: string
@@ -19,7 +20,7 @@ export type SelectProps = Omit<JSX.IntrinsicElements["select"], "children"> & {
 }
 
 export const Select: FC<SelectProps> = (props) => {
-  const { options, placeholder, labelPosition = "above", children, style, ...selectProps } = props
+  const { options, placeholder, labelPosition = "above", children, style, class: className, ...selectProps } = props
 
   // If a label is provided but no id, generate a random id so the label can be clicked
   if (children && !selectProps.id) {
@@ -43,7 +44,7 @@ export const Select: FC<SelectProps> = (props) => {
   }
 
   const selectElement = (
-    <select style={selectStyle} {...selectProps}>
+    <select style={selectStyle} {...selectProps} class={cn("Select", className)}>
       {placeholder && (
         <option value="" disabled>
           {placeholder}
@@ -91,7 +92,7 @@ export const Select: FC<SelectProps> = (props) => {
     return (
       <div style={{ display: "flex", alignItems: "center", gap: "4px", flex: 1 }}>
         {labelElement}
-        <select style={{ ...selectStyle, flex: 1 }} {...selectProps}>
+        <select style={{ ...selectStyle, flex: 1 }} {...selectProps} class={cn("Select", className)}>
           {placeholder && (
             <option value="" disabled>
               {placeholder}
@@ -110,7 +111,7 @@ export const Select: FC<SelectProps> = (props) => {
   if (labelPosition === "right") {
     return (
       <div style={{ display: "flex", alignItems: "center", gap: "4px", flex: 1 }}>
-        <select style={{ ...selectStyle, flex: 1 }} {...selectProps}>
+        <select style={{ ...selectStyle, flex: 1 }} {...selectProps} class={cn("Select", className)}>
           {placeholder && (
             <option value="" disabled>
               {placeholder}
diff --git a/src/stack.tsx b/src/stack.tsx
index a777adc..292f2a9 100644
--- a/src/stack.tsx
+++ b/src/stack.tsx
@@ -6,6 +6,7 @@ import { Section } from "./section"
 import { H2 } from "./text"
 import { RedBox, GreenBox, BlueBox } from "./box"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 export const VStack: FC<VStackProps> = (props) => {
   return (
@@ -15,6 +16,9 @@ export const VStack: FC<VStackProps> = (props) => {
       crossAxis={props.h}
       wrap={props.wrap}
       gap={props.gap}
+      maxWidth={props.maxWidth}
+      gridSizes={props.rows}
+      componentName="VStack"
       class={props.class}
       style={props.style}
     >
@@ -31,6 +35,9 @@ export const HStack: FC<HStackProps> = (props) => {
       crossAxis={props.v}
       wrap={props.wrap}
       gap={props.gap}
+      maxWidth={props.maxWidth}
+      gridSizes={props.cols}
+      componentName="HStack"
       class={props.class}
       style={props.style}
     >
@@ -42,11 +49,37 @@ export const HStack: FC<HStackProps> = (props) => {
 const Stack: FC<StackProps> = (props) => {
   const gapPx = props.gap ? props.gap * 4 : 0
 
+  // Use CSS Grid when gridSizes (cols/rows) is provided
+  if (props.gridSizes) {
+    const gridTemplate = props.gridSizes.map(size => `${size}fr`).join(" ")
+
+    const gridStyles: JSX.CSSProperties = {
+      display: "grid",
+      gap: `${gapPx}px`,
+      maxWidth: props.maxWidth,
+    }
+
+    if (props.direction === "row") {
+      gridStyles.gridTemplateColumns = gridTemplate
+    } else {
+      gridStyles.gridTemplateRows = gridTemplate
+    }
+
+    const combinedStyles = {
+      ...gridStyles,
+      ...props.style,
+    }
+
+    return <div class={cn(props.componentName, props.class)} style={combinedStyles}>{props.children}</div>
+  }
+
+  // Default flexbox behavior
   const baseStyles: JSX.CSSProperties = {
     display: "flex",
     flexDirection: props.direction === "row" ? "row" : "column",
     flexWrap: props.wrap ? "wrap" : "nowrap",
     gap: `${gapPx}px`,
+    maxWidth: props.maxWidth,
   }
 
   if (props.mainAxis) {
@@ -62,7 +95,7 @@ const Stack: FC<StackProps> = (props) => {
     ...props.style,
   }
 
-  return <div class={props.class} style={combinedStyles}>{props.children}</div>
+  return <div class={cn(props.componentName, props.class)} style={combinedStyles}>{props.children}</div>
 }
 
 export const Test = () => {
@@ -78,6 +111,8 @@ export const Test = () => {
           '<VStack gap={4} v="center">...</VStack>',
           '<HStack>...</HStack>',
           '<HStack gap={6} h="between" v="center">...</HStack>',
+          '<HStack cols={[7, 3]} maxWidth="1200px" gap={4}>...</HStack>',
+          '<VStack rows={[2, 1]} maxWidth="800px">...</VStack>',
         ]}
       />
 
@@ -150,6 +185,95 @@ export const Test = () => {
           </Grid>
         </div>
       </VStack>
+
+      {/* Custom column sizing */}
+      <VStack gap={4}>
+        <H2>HStack with Custom Column Sizing</H2>
+        <VStack gap={4}>
+          <div>
+            <div style={{ fontSize: "14px", fontWeight: "500", marginBottom: "8px" }}>
+              cols=[7, 3] (70%/30% split)
+            </div>
+            <HStack cols={[7, 3]} gap={4} style={{ backgroundColor: "#f3f4f6", padding: "16px" }}>
+              <div style={{ backgroundColor: "#bfdbfe", padding: "16px", textAlign: "center" }}>
+                70% width
+              </div>
+              <div style={{ backgroundColor: "#fecaca", padding: "16px", textAlign: "center" }}>
+                30% width
+              </div>
+            </HStack>
+          </div>
+
+          <div>
+            <div style={{ fontSize: "14px", fontWeight: "500", marginBottom: "8px" }}>
+              cols=[2, 1] (66%/33% split)
+            </div>
+            <HStack cols={[2, 1]} gap={4} style={{ backgroundColor: "#f3f4f6", padding: "16px" }}>
+              <div style={{ backgroundColor: "#bbf7d0", padding: "16px", textAlign: "center" }}>
+                2/3 width
+              </div>
+              <div style={{ backgroundColor: "#fef08a", padding: "16px", textAlign: "center" }}>
+                1/3 width
+              </div>
+            </HStack>
+          </div>
+
+          <div>
+            <div style={{ fontSize: "14px", fontWeight: "500", marginBottom: "8px" }}>
+              cols=[1, 2, 1] (25%/50%/25% split)
+            </div>
+            <HStack cols={[1, 2, 1]} gap={4} style={{ backgroundColor: "#f3f4f6", padding: "16px" }}>
+              <div style={{ backgroundColor: "#e9d5ff", padding: "16px", textAlign: "center" }}>
+                25%
+              </div>
+              <div style={{ backgroundColor: "#bfdbfe", padding: "16px", textAlign: "center" }}>
+                50%
+              </div>
+              <div style={{ backgroundColor: "#fbcfe8", padding: "16px", textAlign: "center" }}>
+                25%
+              </div>
+            </HStack>
+          </div>
+
+          <div>
+            <div style={{ fontSize: "14px", fontWeight: "500", marginBottom: "8px" }}>
+              With maxWidth="600px"
+            </div>
+            <HStack cols={[7, 3]} maxWidth="600px" gap={4} style={{ backgroundColor: "#f3f4f6", padding: "16px" }}>
+              <div style={{ backgroundColor: "#bfdbfe", padding: "16px", textAlign: "center" }}>
+                70% of max 600px
+              </div>
+              <div style={{ backgroundColor: "#fecaca", padding: "16px", textAlign: "center" }}>
+                30% of max 600px
+              </div>
+            </HStack>
+          </div>
+        </VStack>
+      </VStack>
+
+      {/* Custom row sizing */}
+      <VStack gap={4}>
+        <H2>VStack with Custom Row Sizing</H2>
+        <VStack gap={4}>
+          <div>
+            <div style={{ fontSize: "14px", fontWeight: "500", marginBottom: "8px" }}>
+              rows=[2, 1] (2/3 and 1/3 height)
+            </div>
+            <VStack
+              rows={[2, 1]}
+              gap={4}
+              style={{ backgroundColor: "#f3f4f6", padding: "16px", height: "300px" }}
+            >
+              <div style={{ backgroundColor: "#bfdbfe", padding: "16px", textAlign: "center" }}>
+                2/3 height
+              </div>
+              <div style={{ backgroundColor: "#fecaca", padding: "16px", textAlign: "center" }}>
+                1/3 height
+              </div>
+            </VStack>
+          </div>
+        </VStack>
+      </VStack>
     </Section>
   )
 }
@@ -162,6 +286,9 @@ type StackProps = {
   crossAxis?: string
   wrap?: boolean
   gap?: TailwindSize
+  maxWidth?: string
+  gridSizes?: number[] // cols for row, rows for col
+  componentName?: string // for data-howl attribute
   class?: string
   style?: JSX.CSSProperties
   children?: any
@@ -173,6 +300,7 @@ type CrossAxisOpts = "start" | "center" | "end" | "stretch" | "baseline"
 type CommonStackProps = PropsWithChildren & {
   wrap?: boolean
   gap?: TailwindSize
+  maxWidth?: string
   class?: string
   style?: JSX.CSSProperties
 }
@@ -180,11 +308,13 @@ type CommonStackProps = PropsWithChildren & {
 type VStackProps = CommonStackProps & {
   v?: MainAxisOpts // main axis for vertical stack
   h?: CrossAxisOpts // cross axis for vertical stack
+  rows?: number[] // custom row sizing (e.g., [7, 3] for 70%/30%)
 }
 
 type HStackProps = CommonStackProps & {
   h?: MainAxisOpts // main axis for horizontal stack
   v?: CrossAxisOpts // cross axis for horizontal stack
+  cols?: number[] // custom column sizing (e.g., [7, 3] for 70%/30%)
 }
 
 function getJustifyContent(axis: string): string {
diff --git a/src/text.tsx b/src/text.tsx
index e9d1041..743d091 100644
--- a/src/text.tsx
+++ b/src/text.tsx
@@ -1,6 +1,7 @@
 import "hono/jsx"
 import type { FC, PropsWithChildren, JSX } from "hono/jsx"
 import { CodeExamples } from "./code"
+import { cn } from "./cn"
 
 type TextProps = PropsWithChildren & {
   class?: string
@@ -8,31 +9,31 @@ type TextProps = PropsWithChildren & {
 }
 
 export const H1: FC<TextProps> = ({ children, class: className, style }) => (
-  <h1 class={className} style={{ fontSize: "24px", fontWeight: "bold", ...style }}>{children}</h1>
+  <h1 class={cn("H1", className)} style={{ fontSize: "24px", fontWeight: "bold", ...style }}>{children}</h1>
 )
 
 export const H2: FC<TextProps> = ({ children, class: className, style }) => (
-  <h2 class={className} style={{ fontSize: "20px", fontWeight: "bold", ...style }}>{children}</h2>
+  <h2 class={cn("H2", className)} style={{ fontSize: "20px", fontWeight: "bold", ...style }}>{children}</h2>
 )
 
 export const H3: FC<TextProps> = ({ children, class: className, style }) => (
-  <h3 class={className} style={{ fontSize: "18px", fontWeight: "600", ...style }}>{children}</h3>
+  <h3 class={cn("H3", className)} style={{ fontSize: "18px", fontWeight: "600", ...style }}>{children}</h3>
 )
 
 export const H4: FC<TextProps> = ({ children, class: className, style }) => (
-  <h4 class={className} style={{ fontSize: "16px", fontWeight: "600", ...style }}>{children}</h4>
+  <h4 class={cn("H4", className)} style={{ fontSize: "16px", fontWeight: "600", ...style }}>{children}</h4>
 )
 
 export const H5: FC<TextProps> = ({ children, class: className, style }) => (
-  <h5 class={className} style={{ fontSize: "14px", fontWeight: "500", ...style }}>{children}</h5>
+  <h5 class={cn("H5", className)} style={{ fontSize: "14px", fontWeight: "500", ...style }}>{children}</h5>
 )
 
 export const Text: FC<TextProps> = ({ children, class: className, style }) => (
-  <p class={className} style={{ fontSize: "14px", ...style }}>{children}</p>
+  <p class={cn("Text", className)} style={{ fontSize: "14px", ...style }}>{children}</p>
 )
 
 export const SmallText: FC<TextProps> = ({ children, class: className, style }) => (
-  <p class={className} style={{ fontSize: "12px", ...style }}>{children}</p>
+  <p class={cn("SmallText", className)} style={{ fontSize: "12px", ...style }}>{children}</p>
 )
 
 export const Test = () => {