Electricity has shaped modern civilization in a way few other discoveries have. Nonetheless, few students successfully develop a basic understanding of voltage, current, and resistance or their mutual relationship in simple DC circuits. Despite teachers' best efforts in the classroom, so-called "alternative conceptions" often prevail after traditional instruction. In particular, voltage has proven to be a difficult concept to teach--many students erroneously think of voltage as a property of electric current. Furthermore, a battery is often considered to be a source of constant current rather than constant voltage. In order to help students develop a better understanding of simple DC circuits, we developed a new curriculum with an accompanying computer simulation that illustrates potential differences in circuits in order to make voltage rather than current the students' primary concept when analyzing circuits. To this end, the curriculum takes typical alternative conceptions into account and builds on students' everyday experiences with air pressure in order to provide them with an immediately tangible counterpart in electric potential. In analogy to air pressure differences that cause an air flow, voltage is introduced as an "electric pressure difference" that causes an electric current. Using the accompanying computer simulation, potential differences are visualized in simple DC circuits using color coding and a height representation. The new curriculum including teaching resources as well as the newly developed computer simulation are both freely available online to teachers and students alike.