Update rounded_corner.md

Author: taohsu

components/control/quantity_input/dsm/guideline/rounded_corner.md

@@ -1,47 +1,3 @@
 **`False`** For a square finish.
 
 **`True`** For a finish with rounded corner. To be favored in more emotional, immersive contexts or those tied to specific visual identities. For standard or business-oriented journeys, keep the default corners. This evolution addresses the need for flexibility in adapting the design to certain brand contexts.
-
-### Do & don'ts
-
-✅ **Do:** Use rounded corners consistently with other form elements in your design system to maintain visual harmony  
-❌ **Don't:** Apply rounded corners to quantity inputs while using square corners on adjacent buttons or fields
-
-✅ **Do:** Reserve rounded corners for consumer-facing or lifestyle brand interfaces where softer aesthetics align with brand identity  
-❌ **Don't:** Use rounded corners in enterprise or data-heavy applications where sharp edges convey precision
-
-✅ **Do:** Consider rounded corners for mobile interfaces where they may improve perceived touch targets  
-❌ **Don't:** Assume rounded corners automatically improve usability—they are primarily a visual treatment
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-✅ **Do:** Document your corner radius choice in design tokens for consistent application across components  
-❌ **Don't:** Mix corner radius values arbitrarily across different quantity input instances
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-✅ **Do:** Test rounded corner variants with your specific button placement (trailing vs. split) to ensure visual balance  
-❌ **Don't:** Apply rounded corners without verifying they work well with increment/decrement button styling
-
----
-
-### Input status
-
-**`Empty`** The Empty state indicates that the quantity input is blank with no content or placeholder, a neutral starting point.
-
-**`Empty (Placeholder)`** The Empty with Placeholder state provides a hint or guidance inside the field to suggest expected input.
-
-**`Filled`** The Filled state shows that the user has entered valid content into the field, replacing any placeholder.
-
-### Do & don'ts
-
-✅ **Do:** Set a sensible default value (typically 1) to reduce user effort and prevent empty submission errors  
-❌ **Don't:** Leave quantity inputs empty in e-commerce contexts where a zero value has no valid meaning
-
-✅ **Do:** Use placeholder text to indicate expected format when the field can be empty (e.g., "Enter quantity")  
-❌ **Don't:** Rely solely on placeholders for critical instructions—they disappear once users begin typing
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-✅ **Do:** Ensure filled state styling provides clear feedback that user input has been captured  
-❌ **Don't:** Style filled and empty states identically, making it difficult to scan form completion status
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-✅ **Do:** Preserve entered values when users navigate away and return to the form  
-❌ **Don't:** Reset quantity values unexpectedly, forcing users to re-enter their selections
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-✅ **Do:** Validate and display the filled state immediately when users type valid numbers  
-❌ **Don't:** Delay visual confirmation of valid input, leaving users uncertain if their entry was accepted