PowerCounter.prototype = {
    value: 0,
    increment: function() {
        if(this.value==0) this.value = 2;
        else this.value *= this.value;
        this.updateValue();
    },
    decrement: function() {
        if(this.value==2) this.value = 0;
        else this.value = Math.sqrt(this.value);
        this.updateValue();
    },
    updateValue: function() {
        this._element.firstChild.innerHTML = this.value;
    }
};