:root {
  color-scheme: light dark;
  font-family: "Inter", "Segoe UI", sans-serif;
  background-color: #111;
  color: #f4f4f4;
  --canvas-aspect: 1.41421356;
  --canvas-fit-height: 88vh;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: radial-gradient(circle at 20% 20%, rgba(255, 255, 255, 0.05), transparent 45%),
              radial-gradient(circle at 80% 0%, rgba(255, 255, 255, 0.08), transparent 55%),
              #0a0a0a;
}

.app-shell {
  width: min(900px, 92vw);
  display: grid;
  gap: 1.5rem;
  padding: 2rem;
  border-radius: 18px;
  background: rgba(20, 20, 20, 0.72);
  box-shadow: 0 18px 42px rgba(0, 0, 0, 0.45);
}

header h1 {
  margin: 0;
  font-size: clamp(1.8rem, 4vw, 2.4rem);
}

header p {
  margin: 0.35rem 0 0;
  opacity: 0.75;
}

.viewport {
  position: relative;
  border-radius: 14px;
  overflow: hidden;
  border: 1px solid rgba(255, 255, 255, 0.12);
  background: rgba(0, 0, 0, 0.65);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}

#crop-canvas {
  width: min(100%, calc(var(--canvas-fit-height) / var(--canvas-aspect)));
  max-height: var(--canvas-fit-height);
  height: auto;
  display: block;
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  align-items: center;
  justify-content: space-between;
}

.controls button {
  all: unset;
  cursor: pointer;
  padding: 0.75rem 1.5rem;
  border-radius: 999px;
  font-weight: 600;
  transition: transform 120ms ease, box-shadow 120ms ease;
}

#pick-folder-btn {
  background: linear-gradient(135deg, #4facfe, #00f2fe);
  color: #0b0b0b;
  box-shadow: 0 10px 18px rgba(79, 172, 254, 0.32);
}

#pick-folder-btn:hover,
#pick-folder-btn:focus-visible {
  transform: translateY(-2px);
  box-shadow: 0 16px 24px rgba(0, 242, 254, 0.30);
}

#shuffle-btn {
  background: linear-gradient(135deg, #ff5f6d, #ffc371);
  color: #1b1b1b;
  box-shadow: 0 12px 20px rgba(255, 95, 109, 0.35);
}

#shuffle-btn:hover,
#shuffle-btn:focus-visible {
  transform: translateY(-2px);
  box-shadow: 0 18px 28px rgba(255, 127, 80, 0.35);
}

#download-btn {
  background: linear-gradient(135deg, #667eea, #764ba2);
  color: #f5f5f5;
  box-shadow: 0 12px 22px rgba(102, 126, 234, 0.35);
}

#download-btn:hover,
#download-btn:focus-visible {
  transform: translateY(-2px);
  box-shadow: 0 18px 30px rgba(118, 75, 162, 0.38);
}

.control-group {
  display: flex;
  gap: 0.75rem;
  align-items: center;
}

.info {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  font-size: 0.95rem;
  opacity: 0.85;
}

@media (max-width: 640px) {
  :root {
    --canvas-fit-height: 72vh;
  }

  .app-shell {
    padding: 1.5rem;
    gap: 1rem;
  }

  .controls {
    align-items: stretch;
  }

  #shuffle-btn {
    flex: 1;
    text-align: center;
  }

  .info {
    width: 100%;
  }
}