function show(platform, enabled, useSettingsInsteadOfPreferences) {
  document.body.classList.add(`platform-${platform}`);

  if (useSettingsInsteadOfPreferences) {
    document.getElementsByClassName('platform-mac state-on')[0].innerText = 'BetterSEQTA+’s extension is currently on. You can turn it off in the Extensions section of Safari Settings.';
    document.getElementsByClassName('platform-mac state-off')[0].innerText = 'BetterSEQTA+’s extension is currently off. You can turn it on in the Extensions section of Safari Settings.';
    document.getElementsByClassName('platform-mac state-unknown')[0].innerText = 'You can turn on BetterSEQTA+’s extension in the Extensions section of Safari Settings.';
    document.getElementsByClassName('platform-mac open-preferences')[0].innerText = 'Quit and Open Safari Settings…';
  }

  if (typeof enabled === 'boolean') {
    document.body.classList.toggle('state-on', enabled);
    document.body.classList.toggle('state-off', !enabled);
  } else {
    document.body.classList.remove('state-on');
    document.body.classList.remove('state-off');
  }
}

function openPreferences() {
  webkit.messageHandlers.controller.postMessage('open-preferences');
}

document.querySelector('button.open-preferences').addEventListener('click', openPreferences);