title: Can't run app projects on Android Studio
body: <p>I am new to Android Studio, and I installed it on Ubuntu 14.04 LTS (64bit).</p>
  
  <p>When I open the project in Android Studio, I get my project files marked with red and the debug configuration button beside the run button is marked with red X as shown in the below image:</p>
  
  <p><a href="https://i.stack.imgur.com/a1UfQ.png" rel="noreferrer"><img src="https://i.stack.imgur.com/a1UfQ.png" alt="enter image description here"></a></p>
  
  <p>Please tell me how to solve this issue.</p>