/* ================================================================
   SPLITTIFY - Core Design System
   ================================================================ */

:root {
  /* Colors */
  --bg-app: #0f172a;
  --bg-surface: #1e293b;
  --bg-surface-hover: #334155;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --accent: #3b82f6;       /* Blue */
  --accent-hover: #2563eb;
  --success: #10b981;      /* Green for "you are owed" */
  --success-bg: rgba(16, 185, 129, 0.1);
  --danger: #ef4444;       /* Red for "you owe" */
  --danger-bg: rgba(239, 68, 68, 0.1);
  --border: rgba(255, 255, 255, 0.08);
  
  /* Typography & Forms */
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --shadow-sm: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -2px rgba(0, 0, 0, 0.15);
}

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

body {
  font-family: var(--font-family);
  background-color: var(--bg-app);
  color: var(--text-primary);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: color 0.15s ease;
}

a:hover {
  color: var(--accent-hover);
}

/* ── Typography ── */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
}

p {
  color: var(--text-secondary);
}

/* ── Forms & Buttons ── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 16px;
  border-radius: var(--radius-md);
  font-size: 0.95rem;
  font-weight: 500;
  border: none;
  cursor: pointer;
  transition: all 0.2s ease;
}

.btn-primary {
  background-color: var(--accent);
  color: #fff;
  box-shadow: var(--shadow-sm);
}

.btn-primary:hover {
  background-color: var(--accent-hover);
  transform: translateY(-1px);
}

.btn-primary:active {
  transform: translateY(0);
}

.btn-secondary {
  background-color: var(--bg-surface-hover);
  color: var(--text-primary);
}

.btn-secondary:hover {
  background-color: rgba(255, 255, 255, 0.15);
}

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
}

.btn-ghost:hover {
  background-color: var(--bg-surface);
  color: var(--text-primary);
}

.form-group {
  margin-bottom: 20px;
}

.form-label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

.form-control {
  width: 100%;
  padding: 12px 14px;
  background-color: var(--bg-app);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 0.95rem;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
  font-family: inherit;
}

.form-control:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

.form-control::placeholder {
  color: #475569;
}

/* ── Layout Utility ── */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ── Surface / Cards ── */
.card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-sm);
}

/* ── Alerts ── */
.alert {
  padding: 12px 16px;
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  margin-bottom: 20px;
  display: none; /* hidden by default */
}

.alert-error {
  background-color: var(--danger-bg);
  color: #fca5a5;
  border: 1px solid rgba(239, 68, 68, 0.2);
}

.alert-success {
  background-color: var(--success-bg);
  color: #6ee7b7;
  border: 1px solid rgba(16, 185, 129, 0.2);
}

/* ── Utilities ── */
.text-success { color: var(--success); }
.text-danger { color: var(--danger); }
.text-muted { color: var(--text-secondary); }
.font-medium { font-weight: 500; }
.font-bold { font-weight: 700; }
.text-center { text-align: center; }
.mt-2 { margin-top: 0.5rem; }
.mt-4 { margin-top: 1rem; }
.mb-2 { margin-bottom: 0.5rem; }
.mb-4 { margin-bottom: 1rem; }
.flex { display: flex; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-2 { gap: 0.5rem; }
.gap-4 { gap: 1rem; }