function incItem(id) {
    var el = document.getElementById(id);
    if (!el) return;
    
    var count = parseInt(el.value);
    if (isNaN(count)) {
        el.value = 1;
    } else {
        el.value = count < 999 ? count + 1 : 999;
    }
    
    setPrice();
    
    return false;
}

function decItem(id) {
    var el = document.getElementById(id);
    if (!el) return;
    
    var count = parseInt(el.value);
    if (isNaN(count)) {
        el.value = 0;
    } else {
        el.value = count > 0 ? count - 1 : 0;
    }
    
    setPrice();
    
    return false;
}

function onCountBlur(sender) {
    var count = parseInt(sender.value);
    if (isNaN(count)) sender.value = 0;
    
    setPrice();
}

function getPrice() {
    var price = 0;
    
    var dev_items = document.getElementById('dev_items');
    if (!dev_items) return price;
    
    var count = parseInt(dev_items.value);
    if (!isNaN(count)) {
        price += 49.95 * count;
    }
    
    var red_items = document.getElementById('red_items');
    if (!red_items) return price;
    
    var count = parseInt(red_items.value);
    if (!isNaN(count)) {
        price += 199.95 * count;
    }
    
    return price;
}

function setPrice() {
    var el = document.getElementById('price');
    if (!el) return price;
    
    var price = getPrice();
    
    if (price == 0) {
        el.innerHTML = '$0.00';
    } else {
        var str = Math.round(price * 100).toString();
        el.innerHTML = '$' + str.substr(0, str.length - 2) + '.' + str.substr(str.length - 2, str.length);
    }
}

function checkForm(form) {
    if (getPrice() == 0) {
        alert('You have not selected any products.');
        return false;
    }
//    if (!form.firstname.value || !form.lastname.value || !form.email.value || !form.captcha.value) {
//        alert('Please, fill all markered fields.');
//        return false;
//    }
//    if (!IsValidEmail(form.email.value)) {
//        alert('Please, correct email address.');
//        return false;
//    }
    return true;
}