The code below submits the form when any checkbox
is marked.
DEMO
<div class="prog">
<legend class="">Genero</legend>
<form action="" method="post">
<input type="checkbox" name="genero" value="acao" onclick="this.form.submit();"> Ação<br>
<input type="checkbox" name="genero" value="aventura" onclick="this.form.submit();"> Aventura<br>
<input type="checkbox" name="genero" value="esportes" onclick="this.form.submit();"> Esportes<br>
<input type="checkbox" name="genero" value="rpg" onclick="this.form.submit();"> RPG<br>
<input type="checkbox" name="genero" value="arcade" onclick="this.form.submit();"> Arcade<br>
</form>
</div>
OBS: Check boxes offer the option to mark more than one item.
If this is the intention HTML should be structured as follows. DEMO
Add to the input name the [], when submitting the form it will be sent as an array..
<div class="prog">
<legend class="">Genero</legend>
<form action="" method="post">
<input type="checkbox" name="genero[]" value="acao"> Ação<br>
<input type="checkbox" name="genero[]" value="aventura"> Aventura<br>
<input type="checkbox" name="genero[]" value="esportes"> Esportes<br>
<input type="checkbox" name="genero[]" value="rpg"> RPG<br>
<input type="checkbox" name="genero[]" value="arcade"> Arcade<br>
<input type="submit" value="Enviar">
</form>
Example in PHP on the page where the action will occur
if(!empty($_POST['genero'])) {
foreach($_POST['genero'] as $item) {
//açãos
}
}