*{
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

body{
  background: #f2f3f5;
  padding-bottom: 50px;
}

/* TOP TABS */
.top-tabs{
  display: flex;
  background: #fff;
  border-bottom: 1px solid #e0e0e0;
  position: sticky;
  top: 0;
  z-index: 10;
}
.top-tabs .tab{
  flex: 1;
  text-align: center;
  padding: 14px 0;
  font-size: 15px;
  color: #777;
  font-weight: 500;
  cursor: pointer;
}
.top-tabs .tab.active{
  color: #000;
  font-weight: 600;
  border-bottom: 3px solid #2563eb;
}

.top-content{ display: none; }
.top-content.active{ display: block; }

/* SECTION TITLE */
.section-title{
  font-size: 18px;
  font-weight: 700;
  padding: 16px 12px 8px 12px;
  color: #333;
}

/* TEST ITEM */
.test-item{
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: #fff;
  margin: 0 12px 10px 12px;
  padding: 16px;
  border-radius: 12px;
  cursor: pointer;
  box-shadow: 0 1px 3px rgba(0,0,0,0.05);
  transition: transform 0.1s;
}
.test-item:active{ transform: scale(0.98); background: #f5f5f5; }

.test-title{
  font-size: 16px;
  font-weight: 600;
  color: #1a1a1a;
}
.test-meta{
  font-size: 13px;
  color: #777;
  margin-top: 4px;
}

.start-btn{
  background: #2563eb;
  color: #fff;
  padding: 8px 16px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 600;
}

/* SUB TABS WRAPPER FOR SCROLL */
.sub-tabs-wrapper{
  background: #fff;
  margin: 12px;
  border-radius: 12px;
  padding: 4px;
  box-shadow: 0 1px 3px rgba(0,0,0,0.05);
  overflow-x: auto; /* makes it scrollable */
}
.sub-tabs-wrapper::-webkit-scrollbar{ display: none; } /* hide scrollbar */

.sub-tabs{
  display: flex;
  gap: 6px;
  width: max-content; /* important for scroll */
}

.sub-tabs .sub-tab{
  padding: 10px 18px;
  font-size: 15px;
  font-weight: 600;
  color: #333;
  border-radius: 8px;
  cursor: pointer;
  white-space: nowrap; /* don't break text */
}
.sub-tabs .sub-tab.active{
  background: #eef2ff;
  color: #2563eb;
}

/* CARD */
.card{
  background: #fff;
  margin: 12px;
  padding: 20px;
  border-radius: 16px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.card-title{
  text-align: center;
  font-size: 22px;
  font-weight: 700;
  color: #2563eb;
  margin-bottom: 8px;
}

.card-desc{
  text-align: center;
  font-size: 15px;
  color: #555;
  margin-bottom: 20px;
}

.info-box{
  background: #f7f8fa;
  padding: 12px 16px;
  border-radius: 8px;
  margin-bottom: 10px;
  font-size: 15px;
  color: #333;
}
.info-box b{
  color: #000;
}

.example{
  text-align: center;
  margin-top: 16px;
  font-size: 15px;
  color: #333;
  font-style: italic;
}
.example b{
  font-style: normal;
  font-weight: 600;
}

/* TAB SWITCH LOGIC */
.tab-content{
  display: none;
}
.tab-content.active{
  display: block;
}