* {
  box-sizing: border-box;
}

:root {
  --bg-gradient-start: #f7fbff;
  --bg-gradient-end: #e9f2ff;
  --text-color: #1f2937;
  --container-bg: #ffffff;
  --container-shadow: rgba(31, 41, 55, 0.12);
  --card-bg: #ffffff;
  --card-border: #d1d5db;
  --card-shadow: rgba(15, 23, 42, 0.12);
  --card-text: #111827;
  --btn-bg: #2563eb;
  --btn-hover: #1d4ed8;
}

:root.dark {
  --bg-gradient-start: #0f172a;
  --bg-gradient-end: #1e293b;
  --text-color: #e2e8f0;
  --container-bg: #1e293b;
  --container-shadow: rgba(0, 0, 0, 0.4);
  --card-bg: #334155;
  --card-border: #475569;
  --card-shadow: rgba(0, 0, 0, 0.3);
  --card-text: #f1f5f9;
  --btn-bg: #3b82f6;
  --btn-hover: #2563eb;
}

body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  font-family: "Helvetica Neue", Arial, sans-serif;
  background: linear-gradient(135deg, var(--bg-gradient-start), var(--bg-gradient-end));
  color: var(--text-color);
  transition: background 0.3s, color 0.3s;
}

.theme-toggle {
  position: fixed;
  top: 1rem;
  right: 1rem;
  width: 44px;
  height: 44px;
  border: 0;
  border-radius: 50%;
  background: var(--container-bg);
  box-shadow: 0 2px 8px var(--container-shadow);
  font-size: 1.3rem;
  cursor: pointer;
  display: grid;
  place-items: center;
  transition: background 0.3s, box-shadow 0.3s;
  z-index: 10;
}

.theme-toggle:hover {
  box-shadow: 0 4px 14px var(--container-shadow);
}

.container {
  width: min(90%, 560px);
  padding: 2rem;
  border-radius: 16px;
  background: var(--container-bg);
  box-shadow: 0 12px 30px var(--container-shadow);
  text-align: center;
  transition: background 0.3s, box-shadow 0.3s;
}

h1 {
  margin-top: 0;
}

button {
  margin-top: 1rem;
  border: 0;
  border-radius: 10px;
  padding: 0.7rem 1rem;
  background: var(--btn-bg);
  color: #fff;
  font-size: 1rem;
  cursor: pointer;
  transition: background 0.3s;
}

button:hover {
  background: var(--btn-hover);
}

.hand {
  margin-top: 1.25rem;
  display: flex;
  justify-content: center;
  gap: 1rem;
}

.card {
  position: relative;
  width: 140px;
  height: 200px;
  border-radius: 14px;
  border: 2px solid var(--card-border);
  background: var(--card-bg);
  box-shadow: 0 8px 18px var(--card-shadow);
  color: var(--card-text);
  transition: background 0.3s, border-color 0.3s, box-shadow 0.3s, color 0.3s;
}

.corner {
  position: absolute;
  display: flex;
  flex-direction: column;
  line-height: 1;
  font-weight: 700;
}

.top-left {
  top: 10px;
  left: 10px;
  align-items: flex-start;
}

.bottom-right {
  right: 10px;
  bottom: 10px;
  transform: rotate(180deg);
  align-items: flex-start;
}

.rank {
  font-size: 1.2rem;
}

.suit {
  font-size: 1rem;
}

.center-suit {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 3rem;
}

.card.red {
  color: #dc2626;
}

.result {
  margin-top: 1rem;
  font-size: 1.1rem;
  font-weight: 700;
}