/* =========================================================
   DESIGN SYSTEM & VARIABLES (DARK / LIGHT THEME)
   ========================================================= */
:root {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: rgba(30, 41, 59, 0.7);
  --bg-input: #0f172a;
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-label: #cbd5e1;
  --accent: #0ea5e9;
  --accent-hover: #0284c7;
  --border-color: rgba(255, 255, 255, 0.1);
  --shadow: 0 10px 25px rgba(0, 0, 0, 0.3);
  --glass-bg: rgba(30, 41, 59, 0.85);
  --glass-border: rgba(255, 255, 255, 0.12);
  --font-family: 'Poppins', system-ui, -apple-system, sans-serif;
}

[data-theme="light"] {
  --bg-primary: #f1f5f9;
  --bg-secondary: #ffffff;
  --bg-card: rgba(255, 255, 255, 0.9);
  --bg-input: #f8fafc;
  --text-main: #0f172a;
  --text-muted: #64748b;
  --text-label: #334155;
  --accent: #0284c7;
  --accent-hover: #0369a1;
  --border-color: rgba(0, 0, 0, 0.1);
  --shadow: 0 10px 25px rgba(0, 0, 0, 0.06);
  --glass-bg: rgba(255, 255, 255, 0.9);
  --glass-border: rgba(0, 0, 0, 0.08);
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  background-color: var(--bg-primary);
  color: var(--text-main);
  font-family: var(--font-family);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* HEADER & NAVBAR */
header {
  width: 100%;
  padding: 16px 8%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: var(--bg-secondary);
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: var(--shadow);
  backdrop-filter: blur(10px);
}

.logo { display: flex; align-items: center; gap: 12px; text-decoration: none; }
.logo i { font-size: 24px; color: var(--accent); }
.logo h2 { color: var(--text-main); font-size: 20px; font-weight: 700; letter-spacing: -0.5px; }

nav { display: flex; align-items: center; gap: 20px; }
.nav-links { display: flex; align-items: center; gap: 24px; list-style: none; }
.nav-links a { position: relative; display: flex; align-items: center; gap: 8px; text-decoration: none; color: var(--text-main); font-size: 15px; font-weight: 500; transition: color 0.3s ease; }
.nav-links a:hover, .nav-links a.active { color: var(--accent); }
.nav-links a::after { content: ""; position: absolute; left: 0; bottom: -6px; width: 0; height: 2px; background-color: var(--accent); transition: width 0.3s ease; }
.nav-links a:hover::after, .nav-links a.active::after { width: 100%; }

.header-actions { display: flex; align-items: center; gap: 12px; }
.btn-icon, .btn-install { background: var(--bg-primary); border: 1px solid var(--border-color); color: var(--text-main); padding: 8px 14px; border-radius: 8px; cursor: pointer; display: inline-flex; align-items: center; gap: 8px; font-size: 14px; font-weight: 500; font-family: inherit; transition: all 0.3s ease; }
.btn-icon { padding: 8px 12px; }
.btn-icon:hover, .btn-install:hover { background: var(--accent); color: #ffffff; border-color: var(--accent); transform: translateY(-2px); }
.btn-install-hidden { display: none !important; }
.hamburger { display: none; background: none; border: none; color: var(--text-main); font-size: 24px; cursor: pointer; padding: 4px; }

/* HERO SECTION */
.hero { width: 100%; flex: 1; padding: 40px 8%; display: flex; justify-content: space-between; align-items: center; gap: 40px; }
.hero-kiri { flex: 1.2; }
.hero-kiri h1 { font-size: 2.8rem; color: var(--text-main); line-height: 1.2; margin-bottom: 12px; font-weight: 700; }
.hero-kiri h1 span { display: block; color: var(--accent); }
.hero-kiri h2 { font-size: 1.4rem; color: var(--text-muted); margin-bottom: 16px; font-weight: 500; }
.hero-kiri p { font-size: 1rem; color: var(--text-muted); line-height: 1.7; max-width: 560px; margin-bottom: 30px; }

.card-container { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 20px; max-width: 520px; }
.card { background: var(--glass-bg); border: 1px solid var(--glass-border); padding: 24px; border-radius: 16px; text-align: center; color: var(--text-main); box-shadow: var(--shadow); backdrop-filter: blur(10px); transition: transform 0.3s ease, box-shadow 0.3s ease; }
.card:hover { transform: translateY(-6px); box-shadow: 0 15px 30px rgba(0, 0, 0, 0.2); }
.card i { font-size: 40px; color: var(--accent); margin-bottom: 12px; }
.card h3 { font-size: 1.2rem; margin-bottom: 6px; }
.card p { font-size: 0.875rem; margin-bottom: 18px; color: var(--text-muted); }
.card .btn { width: 100%; padding: 10px; border: none; border-radius: 8px; background: var(--accent); color: #ffffff; font-size: 14px; font-weight: 600; cursor: pointer; text-decoration: none; display: inline-block; transition: background-color 0.3s ease; }
.card .btn:hover { background: var(--accent-hover); }

.hero-kanan { flex: 1; display: flex; justify-content: center; align-items: center; }
.hero-kanan img { width: 420px; max-width: 100%; height: auto; transform: perspective(1000px) rotateY(-15deg); filter: drop-shadow(0 20px 25px rgba(0,0,0,0.3)); transition: transform 0.5s ease; }
.hero-kanan img:hover { transform: perspective(1000px) rotateY(0deg) scale(1.03); }

/* FORM & INPUT */
.page-wrapper { min-height: calc(100vh - 140px); display: flex; justify-content: center; align-items: center; padding: 40px 20px; }
.form-container { width: 100%; max-width: 800px; background: var(--bg-secondary); border: 1px solid var(--border-color); border-radius: 16px; padding: 32px; box-shadow: var(--shadow); }
.form-header { text-align: center; margin-bottom: 28px; }
.form-header h1 { color: var(--text-main); font-size: 24px; font-weight: 700; margin-bottom: 8px; }
.form-header p { color: var(--text-muted); font-size: 14px; }
.form-columns { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; }
.form-group { margin-bottom: 18px; }
.form-group label { display: flex; align-items: center; gap: 8px; margin-bottom: 8px; font-size: 14px; font-weight: 500; color: var(--text-label); }
.number { width: 22px; height: 22px; background: var(--accent); color: #fff; border-radius: 50%; display: inline-flex; align-items: center; justify-content: center; font-size: 12px; font-weight: 600; }
.form-group input, .form-group select, .form-group textarea { width: 100%; padding: 10px 14px; background: var(--bg-input); border: 1px solid var(--border-color); border-radius: 8px; color: var(--text-main); font-size: 14px; font-family: inherit; outline: none; transition: border-color 0.3s ease; }
.form-group input:focus, .form-group select:focus, .form-group textarea:focus { border-color: var(--accent); }
.input-satuan { display: flex; gap: 10px; align-items: center; }
.input-satuan span { font-size: 13px; color: var(--text-muted); }
.button-area { display: flex; justify-content: space-between; gap: 16px; margin-top: 24px; }
.btn-kembali, .btn-lanjut { padding: 10px 24px; border-radius: 8px; border: none; font-size: 14px; font-weight: 600; cursor: pointer; font-family: inherit; transition: all 0.3s ease; }
.btn-kembali { background: var(--bg-primary); color: var(--text-main); border: 1px solid var(--border-color); }
.btn-lanjut { background: var(--accent); color: #fff; }
.btn-kembali:hover { background: var(--border-color); }
.btn-lanjut:hover { background: var(--accent-hover); }

/* CALCULATOR LAYOUT */
.header-rumus { padding: 20px 8%; background: var(--bg-secondary); border-bottom: 1px solid var(--border-color); display: flex; justify-content: space-between; align-items: center; gap: 20px; }
.header-tengah { text-align: center; }
.header-tengah h1 { font-size: 22px; color: var(--accent); }
.header-tengah p { font-size: 13px; color: var(--text-muted); }
.layout-utama { padding: 30px 8%; display: grid; grid-template-columns: 280px 1fr 300px; gap: 24px; align-items: start; }
.panel-kiri, .panel-kanan, .card-data { background: var(--bg-secondary); border: 1px solid var(--border-color); border-radius: 14px; padding: 20px; box-shadow: var(--shadow); }
.judul-pilih { font-size: 14px; font-weight: 700; color: var(--accent); margin-bottom: 16px; letter-spacing: 0.5px; }
.pilihan { width: 100%; padding: 12px 14px; background: var(--bg-primary); border: 1px solid var(--border-color); border-radius: 10px; color: var(--text-main); text-align: left; margin-bottom: 10px; cursor: pointer; display: flex; align-items: center; justify-content: space-between; font-family: inherit; font-size: 13px; transition: all 0.3s ease; }
.pilihan.active, .pilihan:hover { border-color: var(--accent); background: var(--accent); color: #ffffff; }
.pilihan .nomor { background: rgba(255,255,255,0.2); }
.card-header { display: flex; align-items: center; gap: 12px; margin-bottom: 20px; }
.icon-card, .icon-hasil, .rekap-icon { width: 40px; height: 40px; border-radius: 10px; background: var(--accent); color: #fff; display: flex; align-items: center; justify-content: center; font-size: 18px; }
.tombol-aksi { display: flex; gap: 12px; margin: 20px 0; }
.btn-hitung, .btn-reset { flex: 1; padding: 12px; border-radius: 8px; border: none; font-weight: 600; cursor: pointer; font-family: inherit; display: flex; align-items: center; justify-content: center; gap: 8px; }
.btn-hitung { background: var(--accent); color: #fff; }
.btn-reset { background: var(--bg-primary); color: var(--text-main); border: 1px solid var(--border-color); }
.card-hasil { margin-top: 20px; padding-top: 20px; border-top: 1px solid var(--border-color); }
.hasil-box { background: var(--bg-primary); border: 1px dashed var(--accent); padding: 16px; border-radius: 10px; text-align: center; font-size: 15px; color: var(--text-main); }
.rekap-item { display: flex; justify-content: space-between; padding: 10px 0; border-bottom: 1px solid var(--border-color); font-size: 13px; }

/* FOOTER */
footer { width: 100%; padding: 20px 8%; background-color: var(--bg-secondary); border-top: 1px solid var(--border-color); text-align: center; margin-top: auto; }
footer p { color: var(--text-muted); font-size: 14px; }
footer a { color: var(--accent); text-decoration: none; font-weight: 600; }
footer a:hover { text-decoration: underline; }

/* RESPONSIVE OPTIMIZATION */
@media (max-width: 1024px) {
  .layout-utama { grid-template-columns: 1fr; padding: 20px 5%; }
  .header-rumus { padding: 16px 5%; }
}
@media (max-width: 768px) {
  header { padding: 14px 5%; }
  .hamburger { display: block; }
  .nav-links { position: absolute; top: 100%; left: 0; width: 100%; background-color: var(--bg-secondary); flex-direction: column; align-items: center; gap: 0; max-height: 0; overflow: hidden; transition: max-height 0.3s ease-in-out, padding 0.3s ease; box-shadow: 0 10px 15px rgba(0, 0, 0, 0.2); }
  .nav-links.show { max-height: 300px; padding: 16px 0; }
  .nav-links li { width: 100%; text-align: center; }
  .nav-links a { padding: 12px; justify-content: center; width: 100%; }
  .form-columns { grid-template-columns: 1fr; gap: 12px; }
  .form-container { padding: 20px 16px; }
  .card-container { grid-template-columns: repeat(2, 1fr); gap: 12px; max-width: 100%; }
  .card { padding: 14px 10px; }
  .card i { font-size: 28px; margin-bottom: 6px; }
  .card h3 { font-size: 1rem; }
  .card p { font-size: 0.75rem; margin-bottom: 10px; }
  .card .btn { padding: 8px 6px; font-size: 12px; }
  .hero-kanan img { width: 340px; max-width: 90%; transform: none; margin: 10px auto; }
  .header-rumus { flex-direction: column; text-align: center; gap: 12px; }
  .header-kiri, .header-kanan { width: 100%; justify-content: center; }
  .btn-install span { display: none; }
}