/* ===================== VARIABLES ===================== */
:root {
  --bg: #0f172a;
  --card: #1e293b;
  --muted: #94a3b8;
  --accent: #f1f5f9;
  --key: #334155;
  --key-op: #0ea5e9;
  --key-hover: #475569;
}

/* ===================== GLOBAL ===================== */
* {
  box-sizing: border-box;
}

body {
  font-family: "Segoe UI", Arial, sans-serif;
  margin: 0;
  background: var(--bg);
  color: var(--accent);
  display: flex;
  justify-content: center;
  align-items: flex-start;
  min-height: 100vh;
}

.container {
  max-width: 480px;
  width: 100%;
  background: var(--card);
  border-radius: 16px;
  padding: 25px;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.5);
  margin: 20px;
}

h1 {
  text-align: center;
  font-weight: 700;
  margin: 0 0 20px;
  color: var(--accent);
}

/* ===================== TABS ===================== */
.tabs {
  display: flex;
  gap: 10px;
  margin-bottom: 20px;
  flex-wrap: wrap;
  justify-content: center;
}

.tab {
  padding: 10px 16px;
  border-radius: 12px;
  background: transparent;
  border: 1px solid var(--key);
  cursor: pointer;
  color: var(--accent);
  transition: all 0.3s;
}

.tab:hover {
  background: var(--key-hover);
}

.tab.active {
  background: var(--key-op);
  border-color: var(--key-op);
  color: #fff;
  font-weight: 600;
}

/* ===================== DISPLAY ===================== */
.display {
  height: 70px;
  background: #0f172a;
  border-radius: 12px;
  padding: 12px;
  font-size: 32px;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  box-shadow: inset 0 0 8px rgba(255, 255, 255, 0.1);
  overflow-x: auto;
}

/* ===================== KEYPAD ===================== */
.keypad {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin-top: 15px;
}

.key {
  background: var(--key);
  border-radius: 12px;
  padding: 18px;
  text-align: center;
  font-weight: 600;
  cursor: pointer;
  color: var(--accent);
  transition: all 0.2s;
  font-size: 18px;
  border: none;
}

.key:hover {
  background: var(--key-hover);
}

.key.zero {
  grid-column: span 2;
}

.key.op {
  background: var(--key-op);
  color: #fff;
}

/* ===================== PANELS ===================== */
.panel {
  display: none;
  margin-top: 15px;
  padding: 15px;
  border-radius: 12px;
  background: #1e293b;
  border: 1px solid #334155;
  color: var(--muted);
}

.panel.active {
  display: block;
  color: var(--accent);
}

#basicKeys .keypad {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin-top: 15px;
}

#basicKeys .key {
  background: var(--key);
  border-radius: 12px;
  padding: 18px;
  text-align: center;
  font-weight: 600;
  cursor: pointer;
  color: var(--accent);
  font-size: 18px;
  border: none;
  transition: 0.2s;
}

#basicKeys .key:hover {
  background: var(--key-hover);
}

#basicKeys .key.op {
  background: var(--key-op);
  color: #fff;
}

#basicKeys .key.zero {
  grid-column: span 2;
}


/* ===================== SCIENTIFIC ===================== */
#scientificPanel .keypad {
  grid-template-columns: repeat(4, 1fr);
}

#scientificPanel .key {
  font-size: 16px;
  padding: 14px;
}

/* ===================== PROGRAMMER ===================== */
#programmerPanel .prog-card {
  background: rgba(255, 255, 255, 0.02);
  padding: 20px;
  border-radius: 12px;
  border: 1px solid #334155;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

#programmerPanel label {
  font-size: 14px;
  color: var(--muted);
  margin-bottom: 4px;
}

#programmerPanel input,
#programmerPanel select {
  width: 100%;
  padding: 10px;
  border-radius: 8px;
  border: none;
  background: #0f172a;
  color: #fff;
  font-size: 16px;
}

#programmerPanel button {
  padding: 12px;
  border: none;
  border-radius: 8px;
  background: var(--key-op);
  color: #fff;
  cursor: pointer;
  font-weight: 600;
  transition: background 0.2s;
}

#programmerPanel button:hover {
  background: #0284c7;
}

.prog-results {
  margin-top: 12px;
  padding: 12px;
  background: #1e293b;
  border-radius: 8px;
  font-family: monospace;
}

.prog-results p {
  margin: 6px 0;
  font-size: 15px;
  display: flex;
  justify-content: space-between;
}

.prog-results span {
  font-weight: 600;
  color: var(--key-op);
}


/* ===================== CS TOOLS ===================== */
#cstoolsPanel h3 {
  margin: 12px 0 6px;
  font-size: 16px;
  color: var(--accent);
}

.cs-tool {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 15px;
}

#cstoolsPanel input,
#cstoolsPanel select {
  flex: 1 1 120px;
  padding: 10px;
  border-radius: 8px;
  border: none;
  background: #0f172a;
  color: #fff;
  font-size: 14px;
}

#cstoolsPanel button {
  padding: 10px 16px;
  border: none;
  border-radius: 8px;
  background: var(--key-op);
  color: #fff;
  cursor: pointer;
  font-weight: 600;
  transition: background 0.2s;
}

#cstoolsPanel button:hover {
  background: #0284c7;
}


/* ===================== RESPONSIVE BREAKPOINTS ===================== */

/* ===== 320px – 480px: Small Phones ===== */
@media (min-width: 320px) and (max-width: 480px) {
  .container {
    max-width: 90%;
    padding: 15px;
  }
  .display {
    font-size: 24px;
    height: 60px;
  }
  .key {
    font-size: 14px;
    padding: 12px;
  }
  .tabs {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 5px;
    justify-items: center;
  }
}

/* ===== 481px – 767px: Large Phones / Phablets ===== */
@media (min-width: 481px) and (max-width: 767px) {
  .container {
    max-width: 400px;
    padding: 20px;
  }
  .display {
    font-size: 28px;
  }
  .keypad {
    grid-template-columns: repeat(4, 1fr);
  }
  .tabs {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 5px;
    justify-items: center;
}

/* ===== 768px – 1024px: Tablets ===== */
@media (min-width: 768px) and (max-width: 1024px) {
  .container {
    max-width: 600px;
  }
  .display {
    font-size: 32px;
  }
  .keypad {
    grid-template-columns: repeat(4, 1fr);
  }
}

/* ===== 1024px and Above: Desktops ===== */
@media (min-width: 1025px) {
  .container {
    max-width: 700px;
  }
  .display {
    font-size: 36px;
  }
  .key {
    font-size: 20px;
  }
}
}