/* =========================================================
   VUNA CALCULATOR — David Zasan Elisha
   SEN 482 · Set 2025/26 Software Engineering
   ========================================================= */

/* Google Font — Syne (display) + DM Mono (digits) */
@import url('https://fonts.googleapis.com/css2?family=Syne:wght@700;800&family=DM+Mono:wght@400;500&display=swap');

/* ── CSS Variables ─────────────────────────────────────── */
:root {
  --bg:           #eef0f5;
  --card-bg:      #ffffff;
  --header-bg:    #0f172a;
  --display-bg:   #0f172a;
  --display-text: #f8fafc;
  --accent:       #3b82f6;
  --accent-dark:  #1d4ed8;
  --operator-bg:  #eff6ff;
  --operator-txt: #1d4ed8;
  --number-bg:    #f8fafc;
  --number-txt:   #1e293b;
  --clear-bg:     #fee2e2;
  --clear-txt:    #dc2626;
  --special-bg:   #f0fdf4;
  --special-txt:  #16a34a;
  --equals-bg:    #3b82f6;
  --equals-txt:   #ffffff;
  --shadow-sm:    0 2px 8px rgba(0,0,0,.07);
  --shadow-card:  0 20px 60px rgba(0,0,0,.12);
  --radius-btn:   14px;
  --radius-card:  24px;
}

/* Dark mode overrides */
body.dark-mode {
  --bg:           #0f172a;
  --card-bg:      #1e293b;
  --display-bg:   #020617;
  --operator-bg:  #1e3a5f;
  --operator-txt: #93c5fd;
  --number-bg:    #293548;
  --number-txt:   #e2e8f0;
  --clear-bg:     #3f1212;
  --clear-txt:    #fca5a5;
  --special-bg:   #0f2e1a;
  --special-txt:  #4ade80;
  --equals-bg:    #1d4ed8;
  --shadow-card:  0 20px 60px rgba(0,0,0,.4);
}

/* ── Reset & Base ──────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
  background: var(--bg);
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'DM Mono', monospace;
  transition: background .3s;
}

/* ── Page wrapper ──────────────────────────────────────── */
.page-wrapper {
  width: 100%;
  max-width: 380px;
  padding: 20px 16px;
}

/* ── Header card ───────────────────────────────────────── */
.header-card {
  background: var(--header-bg);
  border-radius: var(--radius-card) var(--radius-card) 0 0;
  padding: 20px 24px 18px;
  text-align: center;
}

.group-header {
  font-family: 'Syne', sans-serif;
  font-size: 1.3rem;
  font-weight: 800;
  letter-spacing: 3px;
  color: #f8fafc;
  text-transform: uppercase;
}

.sub-header {
  font-size: 0.72rem;
  color: #94a3b8;
  margin-top: 4px;
  letter-spacing: 0.3px;
}

/* ── Calculator card ───────────────────────────────────── */
.calculator-card {
  background: var(--card-bg);
  border-radius: 0 0 var(--radius-card) var(--radius-card);
  box-shadow: var(--shadow-card);
  overflow: hidden;
  transition: background .3s;
}

.card-body {
  padding: 24px;
}

/* ── Display ───────────────────────────────────────────── */
.display-container {
  background: var(--display-bg);
  border-radius: 16px;
  padding: 16px 20px;
  margin-bottom: 20px;
}

#result {
  width: 100%;
  background: transparent;
  border: none;
  outline: none;
  color: var(--display-text);
  font-family: 'DM Mono', monospace;
  font-size: 2.2rem;
  font-weight: 500;
  text-align: right;
  caret-color: transparent;
}

#result::placeholder { color: #475569; }

/* ── Button grid ───────────────────────────────────────── */
.btn-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

/* Last row: . 0 =  — equals spans 2 columns */
.btn-grid .btn:nth-last-child(1) { grid-column: span 2; }

/* ── Shared button base ────────────────────────────────── */
.btn {
  height: 62px;
  border: none;
  border-radius: var(--radius-btn);
  font-family: 'DM Mono', monospace;
  font-size: 1.15rem;
  font-weight: 500;
  cursor: pointer;
  transition: transform .12s, box-shadow .12s, filter .12s;
  box-shadow: var(--shadow-sm);
}

.btn:hover  { transform: translateY(-2px); box-shadow: 0 6px 18px rgba(0,0,0,.13); }
.btn:active { transform: translateY(0);    filter: brightness(.92); box-shadow: none; }

/* ── Button variants ───────────────────────────────────── */
.btn-number   { background: var(--number-bg);   color: var(--number-txt); }
.btn-operator { background: var(--operator-bg); color: var(--operator-txt); font-size: 1.3rem; }
.btn-action   { background: var(--clear-bg);    color: var(--clear-txt); }
.btn-special  { background: var(--special-bg);  color: var(--special-txt); }
.btn-equals   { background: var(--equals-bg);   color: var(--equals-txt);
                font-size: 1.4rem; font-weight: 700; }
.btn-equals:hover { filter: brightness(1.1); }

/* ── Theme toggle ──────────────────────────────────────── */
.theme-toggle-btn {
  position: fixed;
  top: 18px;
  right: 18px;
  z-index: 1000;
  background: var(--card-bg);
  border: none;
  border-radius: 50%;
  width: 44px;
  height: 44px;
  font-size: 1.2rem;
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: background .3s;
}

/* ── Responsive ────────────────────────────────────────── */
@media (max-width: 420px) {
  .btn { height: 56px; font-size: 1rem; }
  #result { font-size: 1.8rem; }
  .card-body { padding: 16px; }
}