if timer = 0{background_alpha = 0}
if timer = sec*0.15{background_alpha = 0.1}
if timer = sec*0.30{background_alpha = 0.2}
if timer = sec*0.45{background_alpha = 0.3}
if timer = sec*0.60{background_alpha = 0.4}
if timer = sec*0.75{background_alpha = 0.5}
if timer = sec*0.90{background_alpha = 0.6}
if timer = sec*1.05{background_alpha = 0.7}
if timer = sec*1.20{background_alpha = 0.8}
if timer = sec*1.35{background_alpha = 0.9}
if timer = sec*1.50{background_alpha = 1}