/* ============================================
   Layout
   Header, main grid, panels, responsive
   ============================================ */

/* ---- Header ---- */
.app-header {
  position: sticky;
  top: 0;
  z-index: var(--z-header);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-md) var(--space-xl);
  background: rgba(255, 255, 255, 0.82);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--color-border-light);
}

/* Candy stripe accent bar under header */
.app-header::after {
  content: '';
  position: absolute;
  bottom: -3px;
  left: 0;
  right: 0;
  height: 3px;
  background: repeating-linear-gradient(
    90deg,
    var(--color-candy-pink) 0px,
    var(--color-candy-pink) 8px,
    var(--color-candy-lavender) 8px,
    var(--color-candy-lavender) 16px,
    var(--color-candy-mint) 16px,
    var(--color-candy-mint) 24px,
    var(--color-candy-peach) 24px,
    var(--color-candy-peach) 32px,
    var(--color-candy-sky) 32px,
    var(--color-candy-sky) 40px
  );
  opacity: 0.6;
}

.header-left,
.header-right {
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.header-center {
  flex: 1;
  text-align: center;
}

.brand {
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  line-height: 1.3;
}

.brand-subtitle {
  font-size: 0.78rem;
  color: var(--color-text-tertiary);
  margin-top: 1px;
  letter-spacing: 0.04em;
}

/* ---- Main Content Grid (3 columns) ---- */
.app-main {
  display: grid;
  grid-template-columns: 300px 1fr 320px;
  gap: var(--space-lg);
  max-width: 1600px;
  margin: 0 auto;
  padding: var(--space-lg) var(--space-xl);
  position: relative;
  z-index: 1;
}

.panel-input,
.panel-canvas,
.panel-output {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
}

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

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

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

/* ---- Overlay (backdrop for side panels) ---- */
.overlay {
  position: fixed;
  inset: 0;
  background: rgba(45, 43, 61, 0.25);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--transition-slow), visibility var(--transition-slow);
  z-index: var(--z-overlay);
}

.overlay.open {
  opacity: 1;
  visibility: visible;
}

/* ---- Side Panels (settings, history) ---- */
.side-panel {
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  width: 380px;
  max-width: 90vw;
  background: var(--color-bg-card);
  transform: translateX(-100%);
  transition: transform var(--transition-slow);
  z-index: var(--z-panel);
  box-shadow: var(--shadow-lg);
  display: flex;
  flex-direction: column;
}

.side-panel.side-panel-right {
  left: auto;
  right: 0;
  transform: translateX(100%);
}

.side-panel.open {
  transform: translateX(0);
}

.side-panel-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-lg);
  border-bottom: 1px solid var(--color-border);
  flex-shrink: 0;
}

.side-panel-header h2 {
  font-size: 1.1rem;
  font-weight: 600;
}

.side-panel-body {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

/* ---- Responsive ---- */
@media (max-width: 1280px) {
  .app-main {
    grid-template-columns: 300px 1fr;
    /* Canvas and output stack in the right column */
  }

  .panel-canvas {
    grid-column: 1 / -1;
    order: 3;
  }
}

@media (max-width: 768px) {
  .app-main {
    grid-template-columns: 1fr;
    padding: var(--space-md);
    gap: var(--space-md);
  }

  .panel-canvas {
    order: 2;
  }

  .panel-output {
    order: 3;
  }
}

@media (max-width: 640px) {
  .app-header {
    padding: var(--space-sm) var(--space-md);
  }

  .brand {
    font-size: 1.2rem;
  }

  .brand-subtitle {
    font-size: 0.7rem;
  }

  .side-panel {
    width: 100%;
    max-width: 100vw;
  }
}