:root {
  --bg: #eef3f9;
  --panel: #ffffff;
  --panel-border: #ccd6e4;
  --text: #1e2a36;
  --muted: #5a6a7b;
  --accent: #2f73da;
  --accent-dark: #215db7;
  --good: #178f3f;
  --bad: #c23434;
  --shadow: 0 12px 28px rgba(27, 43, 65, 0.12);
  --radius: 20px;
  --slot-height: 84px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: linear-gradient(180deg, #f7fbff 0%, var(--bg) 100%);
  color: var(--text);
}

.app-shell {
  max-width: 1080px;
  margin: 0 auto;
  padding: 24px;
}

.app-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 24px;
  margin-bottom: 24px;
}

.eyebrow {
  margin: 0 0 8px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--accent);
}

h1, h2 {
  margin: 0;
}

h1 {
  font-size: clamp(2rem, 4vw, 2.8rem);
}

h2 {
  font-size: 1.2rem;
  margin-bottom: 8px;
}

.intro,
.panel-help,
.status-text {
  color: var(--muted);
  line-height: 1.5;
}

.status-panel,
.tray-panel,
.tower-panel {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.status-panel {
  min-width: 240px;
  padding: 18px;
  text-align: center;
}

.bulb {
  display: block;
  margin: 0 auto 8px;
}

.workspace {
  display: grid;
  grid-template-columns: 1.2fr 0.9fr;
  gap: 24px;
}

.tray-panel,
.tower-panel {
  padding: 20px;
}

.tray {
  min-height: 320px;
  padding: 18px;
  display: flex;
  flex-wrap: wrap;
  align-content: flex-start;
  gap: 16px;
  border: 2px dashed #c8d4e5;
  border-radius: 18px;
  background: #f8fbff;
}

.tower {
  display: flex;
  flex-direction: column;
  gap: 8px;
  align-items: center;
  justify-content: flex-start;
  min-height: calc(var(--slot-height) * 7 + 48px);
  padding: 16px 12px;
  border: 2px dashed #c8d4e5;
  border-radius: 18px;
  background: linear-gradient(180deg, #f6faff, #edf4fd);
}

.slot {
  width: min(100%, 280px);
  min-height: var(--slot-height);
  border: 2px dashed rgba(65, 104, 156, 0.22);
  border-radius: 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 4px;
  transition: transform 0.15s ease, border-color 0.15s ease, background 0.15s ease;
}

.slot::after {
  content: "Drop brick here";
  color: #96a7bb;
  font-size: 0.9rem;
}

.slot:has(.brick)::after {
  content: "";
}

.drop-hover {
  border-color: var(--accent);
  background: #e8f1ff;
  transform: scale(1.02);
}

.brick {
  position: relative;
  width: 248px;
  min-height: 72px;
  border: none;
  border-radius: 10px;
  color: #ffffff;
  font-size: 1.2rem;
  font-weight: 700;
  cursor: grab;
  box-shadow: inset 0 -5px 0 rgba(0, 0, 0, 0.16), 0 6px 14px rgba(26, 33, 44, 0.16);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 14px 16px 12px;
  text-align: center;
  user-select: none;
}

.brick:active {
  cursor: grabbing;
}

.brick:focus-visible,
.primary-btn:focus-visible,
.secondary-btn:focus-visible {
  outline: 3px solid #1b4e9b;
  outline-offset: 3px;
}

.stud {
  position: absolute;
  top: -10px;
  width: 22px;
  height: 16px;
  border-radius: 6px 6px 0 0;
  background: rgba(255, 255, 255, 0.22);
  box-shadow: inset 0 -2px 0 rgba(0, 0, 0, 0.16);
}

.stud-1 { left: 28px; }
.stud-2 { left: 82px; }
.stud-3 { right: 82px; }
.stud-4 { right: 28px; }

.controls {
  display: flex;
  justify-content: center;
  gap: 14px;
  margin-top: 24px;
}

.primary-btn,
.secondary-btn {
  border: none;
  border-radius: 999px;
  padding: 14px 24px;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  box-shadow: var(--shadow);
}

.primary-btn {
  background: var(--accent);
  color: #fff;
}

.primary-btn:hover {
  background: var(--accent-dark);
}

.secondary-btn {
  background: #e6edf8;
  color: #20324c;
}

.secondary-btn:hover {
  background: #d7e4f6;
}

.is-correct .tower {
  border-color: rgba(23, 143, 63, 0.4);
}

.is-incorrect .tower {
  border-color: rgba(194, 52, 52, 0.4);
}

@media (max-width: 880px) {
  .app-header,
  .workspace {
    grid-template-columns: 1fr;
    display: grid;
  }

  .app-header {
    align-items: stretch;
  }

  .status-panel {
    min-width: 0;
  }
}

@media (max-width: 560px) {
  .app-shell {
    padding: 16px;
  }

  .brick,
  .slot {
    width: 100%;
  }

  .tray {
    justify-content: center;
  }

  .controls {
    flex-direction: column;
  }
}