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

/* base style */
body {
  font-family: 'Poppins', Arial, Helvetica, sans-serif;
  background: #f8fafc;
  color: #1e293b;
  transition: 0.3s ease;
  line-height: 1.6;
}

/* header */
header {
  text-align: center;
  padding: 35px 20px;
  background: linear-gradient(135deg, #3b82f6, #6366f1);
  color: white;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

header h1 {
  font-size: 28px;
  margin-bottom: 5px;
}

header p {
  opacity: 0.9;
  font-size: 15px;
}

/* layout san container */
.container {
  display: flex;
  min-height: 85vh;
}

/* sidebar */
.sidebar {
  width: 230px;
  background: #ffffff;
  padding: 25px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  border-right: 1px solid #e2e8f0;
}

.sidebar button {
  padding: 12px;
  border: none;
  border-radius: 10px;
  background: #f1f5f9;
  color: #1e293b;
  cursor: pointer;
  transition: 0.25s ease;
  text-align: left;
  font-weight: 500;
}

.sidebar button i {
  margin-right: 6px;
}

.sidebar button:hover {
  background: #3b82f6;
  color: white;
  transform: translateX(6px) scale(1.03);
}

.sidebar button.active {
  background: #3b82f6;
  color: white;
}

/* content */
.content {
  flex: 1;
  padding: 40px;
}

.section {
  animation: fade 0.3s ease-in-out;
}

.hidden {
  display: none;
}

/* cards */
.card {
  background: white;
  padding: 30px;
  border-radius: 14px;
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.08);
  max-width: 650px;
}

/* tags */
.tags span {
  display: inline-block;
  margin: 8px 8px 0 0;
  padding: 6px 12px;
  background: #3b82f6;
  color: white;
  border-radius: 20px;
  font-size: 13px;
}

/* activity grid */
.activity-grid {
  margin-top: 25px;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 15px;
}

.activity-grid button {
  padding: 15px;
  border: none;
  border-radius: 10px;
  background: #e2e8f0;
  cursor: pointer;
  transition: 0.25s;
  font-weight: 500;
}

.activity-grid button:hover {
  background: #3b82f6;
  color: white;
  transform: translateY(-4px);
}

/* output */
.output-container {
  margin-top: 30px;
  border-radius: 10px;
  overflow: hidden;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.08);
}

.output-header {
  background: #0f172a;
  color: #e2e8f0;
  padding: 10px 15px;
  font-size: 14px;
}

.output {
  margin-top: 30px;
  padding: 20px;
  background: #f1f5f9;
  border-radius: 10px;
  min-height: 150px;
  border: 1px solid #e2e8f0;
}

/* calculator */
.calculator-card {
  margin-top: 20px;
  background: white;
  padding: 25px;
  border-radius: 12px;
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.08);
  max-width: 420px;
}

.calculator-card label {
  display: block;
  margin-top: 15px;
  font-weight: 600;
}

.calculator-card input {
  width: 100%;
  padding: 10px;
  margin-top: 5px;
  border-radius: 6px;
  border: 1px solid #cbd5e1;
  transition: 0.2s;
}

.calculator-card input:focus {
  outline: none;
  border-color: #3b82f6;
}

/* button group */
.button-group {
  margin-top: 20px;
  display: flex;
  gap: 10px;
}

.button-group button {
  flex: 1;
  padding: 10px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  background: #3b82f6;
  color: white;
  font-weight: 500;
  transition: 0.2s;
}

.button-group button:hover {
  background: #2563eb;
}

/* result */
.result-box {
  margin-top: 20px;
  padding: 15px;
  background: #f1f5f9;
  border-radius: 8px;
  border: 1px solid #e2e8f0;
}

/* footer */
footer {
  text-align: center;
  padding: 18px;
  background: #0f172a;
  color: #94a3b8;
  font-size: 14px;
}

/* dark mode */
body.dark {
  background: #0f172a;
  color: white;
}

body.dark header {
  background: linear-gradient(135deg, #0f172a, #1e293b);
}

body.dark .sidebar {
  background: #1e293b;
  border-right: none;
}

body.dark .sidebar button {
  background: #334155;
  color: white;
}

body.dark .sidebar button:hover {
  background: #3b82f6;
}

body.dark .content {
  background: #0f172a;
}

body.dark .card {
  background: #1e293b;
}

body.dark .output {
  background: #1e293b;
  border: none;
}

body.dark .calculator-card {
  background: #1e293b;
}

body.dark .result-box {
  background: #334155;
  border: none;
}

/* animation */
@keyframes fade {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* responsive */
@media (max-width: 900px) {
  .container {
    flex-direction: column;
  }

  .sidebar {
    width: 100%;
    flex-direction: row;
    overflow-x: auto;
  }

  .sidebar button {
    flex: 1;
    text-align: center;
  }
}

/* margin sa profile */
.profile {
  margin-bottom: 15px;
}

.profile img {
  width: 110px;
  height: 110px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid #3b82f6;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.15);
}

/* about card */
.about-card {
  max-width: 700px;
}

/* top profile area */
.about-top {
  display: flex;
  align-items: center;
  gap: 20px;
  margin-bottom: 20px;
}

/* profile image */
.profile-img {
  width: 110px;
  height: 110px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid #3b82f6;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.15);
}

/* name + role */
.about-info h2 {
  margin-bottom: 4px;
}

.role {
  color: #64748b;
  font-size: 14px;
}

/* aboout text */
.about-text {
  margin-top: 10px;
  line-height: 1.6;
}

/* skills */
.skill-title {
  margin-top: 25px;
  margin-bottom: 10px;
}

.skills {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.skill span {
  font-size: 14px;
}

.skill-bar {
  width: 100%;
  height: 8px;
  background: #e2e8f0;
  border-radius: 10px;
  margin-top: 5px;
  overflow: hidden;
}

.skill-fill {
  height: 100%;
  border-radius: 10px;
  width: 0;
  transition: width 1.5s ease;
}

/* sa skill colors */
.html {
  width: 0%;
  background: #f97316;
}

.css {
  width: 0%;
  background: #3b82f6;
}

.js {
  width: 0%;
  background: #facc15;
}

/* exercise desc */
.exercise-desc {
  margin-top: 10px;
  color: #64748b;
  max-width: 600px;
}

/* activity card */
.activity-card {
  background: #ffffff;
  padding: 15px;
  border-radius: 10px;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.05);
  transition: 0.3s;
}

.activity-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 25px rgba(0, 0, 0, 0.08);
}

.activity-card button {
  width: 100%;
  padding: 12px;
  border: none;
  border-radius: 8px;
  background: #3b82f6;
  color: white;
  cursor: pointer;
  font-weight: 500;
  margin-bottom: 8px;
}

.activity-card button:hover {
  background: #2563eb;
}

.activity-card p {
  font-size: 13px;
  color: #64748b;
}

/* previewe image */
.preview-img {
  width: 280px;
  border-radius: 10px;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.15);
  margin-bottom: 10px;
}