The sky is static now, but this is just a single-colored box drawn into the canvas. Make it animated, start with a simplest animation possible (rain out of boxes?), add more complex behaviors if you have time (moving with the hero? perspective? multiple layers moving at different speeds?)
The sky is static now, but this is just a single-colored box drawn into the canvas. Make it animated, start with a simplest animation possible (rain out of boxes?), add more complex behaviors if you have time (moving with the hero? perspective? multiple layers moving at different speeds?)