var backgroundImageIndex = 0;
        
function nextImg() {
    backgroundImageIndex++;
    
    if (backgroundImageIndex >= backgroundImages.length) {
        backgroundImageIndex = 0;
    }
    
    document.getElementById('background').src=backgroundImages[backgroundImageIndex];
}

function prevImg() {
    backgroundImageIndex--;
    
    if (backgroundImageIndex < 0) {
        backgroundImageIndex = backgroundImages.length - 1;
    }
    
    document.getElementById('background').src=backgroundImages[backgroundImageIndex];
}

function toggleImg() {
    if (document.getElementById('textblock').style.display=='none') {
        document.getElementById('textblock').style.display='block';
        document.getElementById('menublock').style.display='block';
	document.getElementById('toggleImg').innerHTML='Full image';
    } else {
        document.getElementById('textblock').style.display='none';
        document.getElementById('menublock').style.display='none';
	document.getElementById('toggleImg').innerHTML='Text';
    }
}