* {
  box-sizing: border-box;
}

#exercise-container {
  border: 2px solid #999999;
  padding: 20px;
}

#exercise {
  min-height: 120px;
}

/* =========================
   CONTAINERS
========================= */

.tk-container {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 12px;
  margin: 20px;
  flex-wrap: wrap;
}

/* =========================
   DROP SLOTS
========================= */

.tk-slot {
  width: 98px;
  height: 78px;

  border: 4px dashed #b5b5b5;
  border-radius: 12px;

  display: flex;
  align-items: center;
  justify-content: center;

  background: #fff;

  transition: all 0.15s ease;
}

.tk-slot.filled {
  border-style: solid;
  border-color: #b5b5b5;
  background: #eef2f7;
}

/* Hover Ziel */
.tk-slot.tk-hover {
  box-shadow: 0 0 0 3px rgba(0, 119, 182, 0.25);
  border-color: #0077b6;
}

/* =========================
   FEEDBACK
========================= */

.tk-correct {
  border: 4px solid #2ecc71 !important;
  box-shadow: 0 0 6px rgba(46, 204, 113, 0.4);
}

.tk-wrong {
  border: 4px solid #e74c3c !important;
  box-shadow: 0 0 6px rgba(231, 76, 60, 0.4);
}

/* =========================
   DRAG ITEMS
========================= */

.tk-item {
  width: 84px;
  height: 64px;

  background: #0077b6;
  color: white;

  border-radius: 10px;

  box-shadow: 0 2px 6px rgba(0,0,0,0.15);

  cursor: grab;

  display: flex;
  flex-direction: column;
  justify-content: center;

  text-align: center;

  padding: 0;

  transition: transform 0.15s ease, opacity 0.15s ease;
}

.tk-item:active {
  transform: scale(1.05);
}

.tk-item.dragging {
  opacity: 0.6;
}

/* 🔥 Haupttext (KB, MB, GB etc.) */
.tk-item > div {
  font-size: 22px;
  font-weight: 700;
  line-height: 1.1;
}

/* Untertitel */
.tk-item small {
  font-size: 12px;
  color: rgba(255,255,255,0.8);
  margin-top: 3px;
  height: 14px;
}

.tk-item small.placeholder {
  visibility: hidden;
}

/* =========================
   FACTOR INPUTS
========================= */

.tk-factor-block {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 18px;
}

.tk-factor {
  width: 95px;
  padding: 10px;

  font-size: 18px;
  text-align: center;

  border-radius: 6px;
  border: 1px solid #ccc;
}

.tk-hidden {
  display: none;
}

.tk-arrow {
  font-size: 20px;
  opacity: 0.6;
}

/* =========================
   BUTTONS
========================= */

.tk-actions {
  display: flex;
  justify-content: center;
  gap: 12px;
  margin: 20px;
}

/* =========================
   NUMBER INPUT FIX
========================= */

input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

input[type="number"] {
  -moz-appearance: textfield;
}