<%= form_for([@game, @game.guesses.build]) do |f| %>
  <%# with service model, this will be @errors, assigned in controller %>
  <% if @errors and @errors.any? %>
    <div id="error_explanation">
      <h2><%= t("%{errors} prohibited this %{thing} from being saved", errors: t(:error, count: @errors.count), thing: Guess.model_name.human.downcase) %>:</h2>

      <ul>
      <% @errors.full_messages.each do |message| %>
        <li><%= message %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="guess">
    <%= f.label :guess %>
    <%= f.text_field :guess %>
  </div>

  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

<%= form_for([@game, @game.guesses.build]) do |f| %>
  <%# with service model, this will be @errors, assigned in controller %>
  <% if @errors and @errors.any? %>
    <div id="error_explanation">
      <h2><%= t("%{errors} prohibited this %{thing} from being saved", errors: t(:error, count: @errors.count), thing: Guess.model_name.human.downcase) %>:</h2>

      <ul>
      <% @errors.full_messages.each do |message| %>
        <li><%= message %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="guess">
    <%= f.label :guess %>
    <%= f.text_field :guess, maxlength: 1 %>
  </div>

  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

Add max length for guess
Add max length for guess
