I've created a mobile-first translator app with the following features:

Key Features:

1. Language Selection: Support for 12 languages including Korean (한국어)
2. Real-time Speech Recognition: Uses Web Speech API to convert speech to text
3. Live Text Display: Shows spoken text in real-time as you speak
4. Translation: Translate button converts text to selected target language
5. Text-to-Speech: Audio playback of translated text
6. Language Swap: Quick button to swap source and target languages

Mobile-Optimized Design:

• Touch-friendly buttons with adequate spacing
• Responsive layout that works on all screen sizes
• Large text areas for easy reading
• Visual feedback with recording indicator and loading states
• Gradient background for modern appearance
• Card-based layout for clear content separation

Technical Features:

• Real-time speech recognition with interim results
• Visual recording indicator with pulsing red dot
• Loading states for translation process
• Error handling for speech recognition
• Clear/reset functionality
• Language flags and names for better UX

Usage:

1. Select source and target languages
2. Tap the microphone button to start recording
3. Speak into your device's microphone
4. See your speech converted to text in real-time
5. Tap "번역하기" (Translate) to translate the text
6. Tap the speaker icon to hear the translation

Note: This demo uses mock translation for demonstration. In a production app, you would integrate with a real translation API like Google Translate, Azure Translator, or similar services.

The app is fully responsive and optimized for mobile devices with Korean language support as requested!