/* Apple-like Design System CSS (iOS-inspired) */
:root {
  --color-bg: #f5f5f7; /* gray-100 */
  --color-surface: #ffffff;
  --color-text-primary: #000000;
  --color-text-secondary: #3c3c4399;
  --color-primary: #d946ef; /* Pink-Purple */
  --font-system: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", Roboto, Oxygen,
    Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif;

  --radius: 12px;
  --shadow-light: 0 8px 24px rgb(0 0 0 / 0.08);
  --shadow-subtle: 0 1px 3px rgb(0 0 0 / 0.1);
  --transition-speed: 0.3s;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font-system);
  background-color: var(--color-bg);
  color: var(--color-text-primary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  line-height: 1.5;
  min-height: 100vh;
  padding: 1rem;
  transition: background-color var(--transition-speed), color var(--transition-speed);
}

/* Headings */
h1, h2, h3, h4, h5 {
  font-weight: 600;
  margin-top: 1.5rem;
  margin-bottom: 0.5rem;
  color: var(--color-text-primary);
  letter-spacing: -0.01em;
}

h1 { font-size: 2.25rem; }
h2 { font-size: 1.75rem; }

p {
  font-weight: 400;
  color: var(--color-text-secondary);
  margin-bottom: 1rem;
}

/* Card / Surface */
.os-card {
  background-color: var(--color-surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow-light);
  padding: 1.5rem 2rem;
  margin-bottom: 2rem;
  transform: translateY(0);
  transition: box-shadow var(--transition-speed), transform var(--transition-speed);
}

.os-card:hover {
  box-shadow: 0 14px 40px rgb(0 0 0 / 0.12);
  transform: translateY(-4px);
}

/* Buttons */
.os-btn {
  font-weight: 600;
  font-size: 1rem;
  padding: 0.6rem 1.4rem;
  border-radius: 14px;
  border: none;
  cursor: pointer;
  user-select: none;
  background-color: var(--color-primary);
  color: white;
  display: inline-block;
  text-align: center;
  line-height: 1;
  box-shadow: var(--shadow-subtle);
  transition:
    background-color var(--transition-speed),
    box-shadow var(--transition-speed),
    transform 0.15s ease;
  -webkit-tap-highlight-color: transparent;
}

.os-btn:focus-visible {
  outline: 3px solid rgba(217, 70, 239, 0.5);
  outline-offset: 2px;
}

.os-btn:hover {
  background-color: #c026d3;
  box-shadow: 0 8px 20px rgba(192, 38, 211, 0.4);
  transform: translateY(-2px);
}

.os-btn:active {
  background-color: #a21caf;
  box-shadow: none;
  transform: translateY(0);
}

/* Input */
.os-input {
  width: 100%;
  padding: 0.7rem 1rem;
  border-radius: var(--radius);
  border: 1.5px solid #d1d1d6;
  font-size: 1rem;
  font-weight: 400;
  color: var(--color-text-primary);
  background-color: var(--color-surface);
  transition:
    border-color var(--transition-speed),
    box-shadow var(--transition-speed),
    transform var(--transition-speed);
}

.os-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 8px rgba(217, 70, 239, 0.4);
  transform: scale(1.01);
}

/* Accordion */
.os-accordion {
  border-radius: var(--radius);
  overflow: hidden;
  background-color: var(--color-surface);
  box-shadow: var(--shadow-subtle);
  transition: box-shadow var(--transition-speed), transform var(--transition-speed);
}

.os-accordion:hover {
  transform: translateY(-2px);
}

.os-accordion:not(:last-child) {
  margin-bottom: 1rem;
}

.os-accordion-header {
  padding: 1rem 1.5rem;
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--color-text-primary);
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  user-select: none;
  border-bottom: 1px solid #e2e2e7;
  transition: background-color var(--transition-speed);
}

.os-accordion-header:hover {
  background-color: #f0f0f5;
}

.os-accordion-header:focus-visible {
  outline: 3px solid rgba(217, 70, 239, 0.5);
  outline-offset: 2px;
}

.os-accordion-content {
  padding: 0 1.5rem;
  font-weight: 400;
  color: var(--color-text-secondary);
  max-height: 0;
  overflow: hidden;
  transition:
    max-height 0.35s cubic-bezier(0.4, 0, 0.2, 1),
    padding 0.35s ease;
}

.os-accordion.active .os-accordion-content {
  max-height: 1000px;
  padding-top: 1rem;
  padding-bottom: 1rem;
}

.os-icon {
  transition: transform 0.35s ease;
  width: 18px;
  height: 18px;
  stroke: var(--color-primary);
  stroke-width: 2;
  fill: none;
}

.os-accordion.active .os-icon {
  transform: rotate(90deg);
  stroke-width: 3;
}

/* Scrollbar */
.os-accordion-content::-webkit-scrollbar {
  width: 8px;
}
.os-accordion-content::-webkit-scrollbar-thumb {
  background-color: rgba(0,0,0,0.1);
  border-radius: 4px;
}
.os-accordion-content::-webkit-scrollbar-track {
  background-color: transparent;
}

/* Utility */
.text-center { text-align: center; }
.mt-4 { margin-top: 1rem; }
.mb-4 { margin-bottom: 1rem; }