:root {
  /* Light Mode (Default) */
  --bg-color: oklch(98% 0.01 250);
  --text-color: oklch(20% 0.02 250);
  --card-bg: oklch(100% 0 0);
  --card-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
  --number-bg: oklch(94% 0.02 250);
  --number-text: oklch(20% 0.02 250);
  --primary-color: oklch(65% 0.2 250);
  --primary-hover: oklch(55% 0.2 250);
  --primary-text: oklch(100% 0 0);
  --border-color: oklch(90% 0.02 250);
  --accent-color: oklch(70% 0.2 320);

  --transition-speed: 0.3s;
}

body.dark-theme {
  /* Dark Mode */
  --bg-color: oklch(12% 0.02 250);
  --text-color: oklch(98% 0.01 250);
  --card-bg: oklch(18% 0.03 250);
  --card-shadow: 0 10px 40px rgba(0, 0, 0, 0.4);
  --number-bg: oklch(25% 0.04 250);
  --number-text: oklch(95% 0.02 250);
  --primary-color: oklch(75% 0.15 250);
  --primary-hover: oklch(85% 0.15 250);
  --primary-text: oklch(10% 0.02 250);
  --border-color: oklch(30% 0.04 250);
  --accent-color: oklch(80% 0.15 320);
}

* {
  box-sizing: border-box;
  transition: background-color var(--transition-speed), color var(--transition-speed), border-color var(--transition-speed), box-shadow var(--transition-speed);
}

body {
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 20px;
}

h1 {
  margin-bottom: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

/* Theme Toggle Button Style */
.theme-toggle {
  position: fixed;
  top: 20px;
  right: 20px;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  color: var(--text-color);
  padding: 10px;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--card-shadow);
  z-index: 1000;
  width: 45px;
  height: 45px;
}

.theme-toggle:hover {
  transform: scale(1.1);
}

.theme-toggle svg {
  width: 24px;
  height: 24px;
  fill: currentColor;
}