Since most password schemes are vulnerable to login-recording attacks, graphical password schemes that are resistant to such attacks have been proposed. However, none of existing graphical password schemes with resistance to login-recording attacks can provide both sufficient security and good usability. Herein, we design and implement a simple sector-based graphical password scheme, RiS, with dynamically adjustable resistance to login-recording attacks. RiS is a pure graphical password scheme by using the shape of the sector. In RiS, the user can dynamically choose the login mode with suitable resistance to login-recording attacks depending on the login environment. Hence, the user can efficiently complete the login process in an environment under low threat of login-recording attacks and securely complete the login process in an environment under high threat of login-recording attacks. Finally, we show that RiS can achieve both sufficient security and good usability.