I figured it was broken (on my browser) too, and I didn't know how to get to other levels. After seeing your comment I went back and saw that touching the rect

I figured it was broken (on my browser) too, and I didn't know how to get to other levels. After seeing your comment I went back and saw that touching the rectangle with the yellow glow takes me to the next level. (On the first level this requires a jump, which is done with the up-arrow key.)