ui <- function() {
  bslib::page(
    fillable = FALSE,
    theme    = bslib::bs_theme(version = 5, primary = "#f59e0b"),
    lang     = "de",
    title    = "Beekeeper",

    shiny::tags$style(shiny::HTML("
      body { background: #fafaf9; }
      .bk-header {
        background: #78350f; color: white;
        position: sticky; top: 0; z-index: 100;
        padding: .75rem 1rem;
        box-shadow: 0 2px 8px rgba(0,0,0,.3);
        min-height: 56px;
      }
      .bk-header h5 { color: white; margin: 0; font-size: 1.05rem; font-weight: 600; }
      .bk-header h4 { color: white; margin: 0; font-size: 1.2rem; font-weight: 700; letter-spacing: -.01em; }
      .bk-header .btn-link {
        color: rgba(255,255,255,.9) !important; text-decoration: none;
      }
      .bk-header-icon {
        padding: .35rem .45rem; border-radius: .4rem; line-height: 1; flex-shrink: 0;
      }
      .bk-header-icon:hover { background: rgba(255,255,255,.18) !important; color: white !important; }
      .collapse-toggle { cursor: pointer; user-select: none; }
      .collapse-toggle .collapse-chevron { transition: transform .2s ease; }
      .collapse-toggle:not(.collapsed) .collapse-chevron { transform: rotate(180deg); }
      .bk-content { max-width: 680px; margin: 0 auto; padding: 1rem 1rem 4rem; }
      .tap-card { cursor: pointer; transition: box-shadow .15s; }
      .tap-card:hover { box-shadow: 0 0 0 3px #f59e0b44; }
      .tap-card:active { box-shadow: 0 0 0 3px #f59e0b; }
      .action-btn {
        display: flex; flex-direction: column;
        align-items: center; justify-content: center;
        height: 80px; gap: .35rem;
        font-size: .82rem; font-weight: 600;
        border-radius: 12px;
      }
      .action-btn .fa, .action-btn .fas, .action-btn .far { font-size: 1.4rem; }
      .stepper-val {
        min-width: 2.8rem; display: inline-block;
        text-align: center; font-size: 1.3rem; font-weight: 700;
      }
      .bk-check .form-check { margin: 0; }
      .bk-check .form-check-input {
        width: 3em; height: 1.5em; margin-top: 0; cursor: pointer;
      }
      .add-dashed {
        border: 2px dashed #ccc; background: transparent;
        border-radius: 8px; cursor: pointer; width: 100%;
        min-height: 100px; color: #888;
        display: flex; align-items: center; justify-content: center;
        gap: .5rem; flex-direction: column; font-weight: 600;
      }
      .add-dashed:hover { border-color: #f59e0b; color: #f59e0b; background: #fffbeb; }
      .leaflet-container { border-radius: 8px; }
      .leaflet-top, .leaflet-bottom { z-index: 50 !important; }
      #ss-connect-dialog, .shiny-disconnected-overlay { display: none !important; }
    ")),

    shiny::tags$script(shiny::HTML("
      $(document).on('shown.bs.modal', function() {
        setTimeout(function() { window.dispatchEvent(new Event('resize')); }, 150);
      });

      history.pushState({bk: true}, '');
      window.addEventListener('popstate', function() {
        history.pushState({bk: true}, '');
        if (window.Shiny) Shiny.setInputValue('nav_back', Date.now(), {priority: 'event'});
      });

      setInterval(function() {
        if (window.Shiny && Shiny.shinyapp && Shiny.shinyapp.isConnected())
          Shiny.setInputValue('keepalive_ping', Date.now());
      }, 25000);
    ")),
    shiny::uiOutput("nav_header"),
    shiny::div(class = "bk-content",
      shiny::uiOutput("screen_content")
    )
  )
}