protected function setMode()
    {
        $this->outerStyle = [
            'display'          => 'none',
            'z-index'          => 10000,
            'position'         => 'fixed',
            'background-color' => '#fff',
            'font-size'        => '12px',
            'color'            => '#000'
        ];
        $this->innerStyle = ['margin' => '10px'];
        $this->buttonStyle = ['margin-left' => '10px'];

        switch ($this->mode) {
            case 'bottom':
                $this->outerStyle = array_merge(
                                        $this->outerStyle, 
                                        [
                                            'bottom'     => 0,
                                            'left'       => 0,
                                            'width'      => '100%',
                                            'box-shadow' => '0 -2px 2px #000',
                                        ]
                                    );
                break;
            case 'box':
                $this->outerStyle = array_merge(
                                        $this->outerStyle, 
                                        [
                                            'bottom'        => '20px',
                                            'right'         => '20px',
                                            'width'         => '300px',
                                            'box-shadow'    => '-2px 2px 2px #000',
                                            'border-radius' => '10px',
                                        ]
                                    );
                break;
            case 'custom':
                $this->outerStyle = [];
                $this->innerStyle = [];
                $this->buttonStyle = [];
                break;
            case 'top':
            default:
                $this->outerStyle = array_merge(
                                        $this->outerStyle, 
                                        [
                                            'top'        => 0,
                                            'left'       => 0,
                                            'width'      => '100%',
                                            'box-shadow' => '0 2px 2px #000',
                                        ]
                                    );
        }
    }