09Bottom tab bar

<main class="stage is-demo">
  <nav class="tabbar" aria-label="Bottom navigation">
    <button class="tab is-active" type="button" aria-current="page"><span class="tab__ic" aria-hidden="true"></span><span class="tab__label">Home</span></button>
    <button class="tab" type="button"><span class="tab__ic" aria-hidden="true"></span><span class="tab__label">Search</span></button>
    <button class="tab" type="button"><span class="tab__ic" aria-hidden="true"></span><span class="tab__label">Saved</span></button>
    <button class="tab" type="button"><span class="tab__ic" aria-hidden="true"></span><span class="tab__label">My page</span></button>
    <span class="indicator" aria-hidden="true"></span>
  </nav>
</main>

@use "../../../../site/static/demo-tokens" as *;

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-quick;      // 220ms — 인디케이터가 옆 탭으로 미끄러지는 시간
$easing: $ease-spring;
$color: $subject-cream;     // 활성 탭 강조색

// ── 데모 무대 ───────────────────────────────────────────
@include stage($stage-ink);

.tabbar {
  position: relative;
  display: flex;
  width: min(92vw, 320px);
  border-radius: $r-card;
  background: rgba($stage-paper, .06);
  padding: $sp-1;
  box-sizing: border-box;
}

.tab {
  flex: 1;
  display: flex; flex-direction: column; align-items: center; gap: $sp-1;
  border: 0; background: transparent; cursor: pointer;
  padding: $sp-2 $sp-1;
  color: $stage-paper;
  font-family: inherit;
  -webkit-tap-highlight-color: transparent;
}
.tab__ic {
  width: $sp-4; height: $sp-4;
  border-radius: 50%;
  background: currentColor;
  opacity: .5;
  transform: scale(1);
  transition: opacity $duration $easing, transform $duration $easing;
}
.tab__label {
  font-weight: 500;
  font-size: 10px;
  line-height: 1;
  font-family: inherit;
  opacity: .55;
  transform: translateY(0);
  transition: opacity $duration $easing, transform $duration $easing;
}
.tab.is-active {
  color: $color;
  .tab__ic    { opacity: 1; transform: scale(1.15); }
  .tab__label { opacity: 1; transform: translateY(-2px); }
}

.indicator {
  position: absolute; left: $sp-1; bottom: $sp-1;
  width: calc(25% - #{$sp-1});
  height: 3px;
  border-radius: $r-xs;
  background: $color;
  transform: translateX(0);
  transition: transform $duration $easing;
}

// 데모 루프: 인디케이터가 네 탭을 순서대로 돌고, 각 탭은 도착하는 구간에서만 밝아진다
.stage.is-demo .indicator { animation: indicator-loop $dur-loop $easing infinite; }
.stage.is-demo .tab:nth-child(1) .tab__ic { animation: tab-ic-loop $dur-loop $easing infinite; animation-delay: 0ms; }
.stage.is-demo .tab:nth-child(2) .tab__ic { animation: tab-ic-loop $dur-loop $easing infinite; animation-delay: 500ms; }
.stage.is-demo .tab:nth-child(3) .tab__ic { animation: tab-ic-loop $dur-loop $easing infinite; animation-delay: 1000ms; }
.stage.is-demo .tab:nth-child(4) .tab__ic { animation: tab-ic-loop $dur-loop $easing infinite; animation-delay: 1500ms; }
.stage.is-demo .tab:nth-child(1) .tab__label { animation: tab-label-loop $dur-loop $easing infinite; animation-delay: 0ms; }
.stage.is-demo .tab:nth-child(2) .tab__label { animation: tab-label-loop $dur-loop $easing infinite; animation-delay: 500ms; }
.stage.is-demo .tab:nth-child(3) .tab__label { animation: tab-label-loop $dur-loop $easing infinite; animation-delay: 1000ms; }
.stage.is-demo .tab:nth-child(4) .tab__label { animation: tab-label-loop $dur-loop $easing infinite; animation-delay: 1500ms; }

@keyframes indicator-loop {
  0%, 20%  { transform: translateX(0); }
  25%, 45% { transform: translateX(100%); }
  50%, 70% { transform: translateX(200%); }
  75%, 95% { transform: translateX(300%); }
  100%     { transform: translateX(0); }
}
@keyframes tab-ic-loop {
  0%, 20%   { opacity: 1; transform: scale(1.15); }
  25%, 100% { opacity: .5; transform: scale(1); }
}
@keyframes tab-label-loop {
  0%, 20%   { opacity: 1; transform: translateY(-2px); }
  25%, 100% { opacity: .55; transform: translateY(0); }
}

@media (prefers-reduced-motion: reduce) {
  .stage.is-demo .indicator,
  .stage.is-demo .tab .tab__ic,
  .stage.is-demo .tab .tab__label { animation: none; }
  .indicator, .tab__ic, .tab__label { transition-duration: 1ms; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.tabbar {
  position: relative;
  display: flex;
  width: min(92vw, 320px);
  border-radius: 16px;
  background: rgba(255, 255, 255, 0.06);
  padding: 4px;
  box-sizing: border-box;
}

.tab {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  border: 0;
  background: transparent;
  cursor: pointer;
  padding: 8px 4px;
  color: #ffffff;
  font-family: inherit;
  -webkit-tap-highlight-color: transparent;
}

.tab__ic {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: currentColor;
  opacity: 0.5;
  transform: scale(1);
  transition: opacity 220ms cubic-bezier(0.2, 0.8, 0.2, 1), transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.tab__label {
  font-weight: 500;
  font-size: 10px;
  line-height: 1;
  font-family: inherit;
  opacity: 0.55;
  transform: translateY(0);
  transition: opacity 220ms cubic-bezier(0.2, 0.8, 0.2, 1), transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.tab.is-active {
  color: #fff7e6;
}
.tab.is-active .tab__ic {
  opacity: 1;
  transform: scale(1.15);
}
.tab.is-active .tab__label {
  opacity: 1;
  transform: translateY(-2px);
}

.indicator {
  position: absolute;
  left: 4px;
  bottom: 4px;
  width: calc(25% - 4px);
  height: 3px;
  border-radius: 4px;
  background: #fff7e6;
  transform: translateX(0);
  transition: transform 220ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.stage.is-demo .indicator {
  animation: indicator-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

.stage.is-demo .tab:nth-child(1) .tab__ic {
  animation: tab-ic-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 0ms;
}

.stage.is-demo .tab:nth-child(2) .tab__ic {
  animation: tab-ic-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 500ms;
}

.stage.is-demo .tab:nth-child(3) .tab__ic {
  animation: tab-ic-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 1000ms;
}

.stage.is-demo .tab:nth-child(4) .tab__ic {
  animation: tab-ic-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 1500ms;
}

.stage.is-demo .tab:nth-child(1) .tab__label {
  animation: tab-label-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 0ms;
}

.stage.is-demo .tab:nth-child(2) .tab__label {
  animation: tab-label-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 500ms;
}

.stage.is-demo .tab:nth-child(3) .tab__label {
  animation: tab-label-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 1000ms;
}

.stage.is-demo .tab:nth-child(4) .tab__label {
  animation: tab-label-loop 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 1500ms;
}

@keyframes indicator-loop {
  0%, 20% {
    transform: translateX(0);
  }
  25%, 45% {
    transform: translateX(100%);
  }
  50%, 70% {
    transform: translateX(200%);
  }
  75%, 95% {
    transform: translateX(300%);
  }
  100% {
    transform: translateX(0);
  }
}
@keyframes tab-ic-loop {
  0%, 20% {
    opacity: 1;
    transform: scale(1.15);
  }
  25%, 100% {
    opacity: 0.5;
    transform: scale(1);
  }
}
@keyframes tab-label-loop {
  0%, 20% {
    opacity: 1;
    transform: translateY(-2px);
  }
  25%, 100% {
    opacity: 0.55;
    transform: translateY(0);
  }
}
@media (prefers-reduced-motion: reduce) {
  .stage.is-demo .indicator,
  .stage.is-demo .tab .tab__ic,
  .stage.is-demo .tab .tab__label {
    animation: none;
  }
  .indicator, .tab__ic, .tab__label {
    transition-duration: 1ms;
  }
}

(function () {
  var stage = document.querySelector('.stage');
  var tabs = document.querySelectorAll('.tab');
  var indicator = document.querySelector('.indicator');
  tabs.forEach(function (tab, i) {
    tab.addEventListener('click', function () {
      stage.classList.remove('is-demo');
      tabs.forEach(function (t) { t.classList.remove('is-active'); t.removeAttribute('aria-current'); });
      tab.classList.add('is-active'); tab.setAttribute('aria-current', 'page');
      indicator.style.transform = 'translateX(' + (i * 100) + '%)';
    });
  });
})();

import { useState } from "react";
import type { CSSProperties } from "react";
import styles from "./BottomTabBar.module.scss";

export type BottomTabBarProps = {
  duration?: number;
  easing?: string;
  color?: string;
};

const TABS = ["홈", "검색", "찜", "마이"];

export default function BottomTabBar({
  duration = 220,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#fff7e6",
}: BottomTabBarProps) {
  const [active, setActive] = useState(0);

  const vars: CSSProperties = {
    "--duration": `${duration}ms`,
    "--easing": easing,
    "--color": color,
    "--i": active,
  };

  return (
    <div className={styles.stage} style={vars}>
      <nav className={styles.tabbar} aria-label="하단 내비게이션">
        {TABS.map((label, i) => (
          <button
            key={label}
            className={styles.tab}
            type="button"
            data-active={i === active}
            aria-current={i === active ? "page" : undefined}
            onClick={() => setActive(i)}
          >
            <span className={styles.ic} aria-hidden="true" />
            <span className={styles.label}>{label}</span>
          </button>
        ))}
        <span className={styles.indicator} aria-hidden="true" />
      </nav>
    </div>
  );
}