:root {
    --bg: #181a1b;
    --fg: #e6e9ef;
    --accent: #3bb3e0;
    --border: #35363a;
    --step-bg: #232429;
    --step-alt: #203750;
    --note-bg: #21303e;
    --input-bg: #18233a;
    --output-bg: #1e2e3d;
    --arrow: #3bb3e0;
    }
    body {
    margin: 0;
    font-family: 'Segoe UI', Arial, sans-serif;
    background: var(--bg);
    color: var(--fg);
    min-height: 100vh;
    transition: background .3s, color .3s;
    }
    .light {
    --bg: #fff;
    --fg: #15181c;
    --accent: #286ea0;
    --border: #c1c2c7;
    --step-bg: #f3f4f7;
    --step-alt: #e6f6ff;
    --note-bg: #e2edf6;
    --input-bg: #eaf4fc;
    --output-bg: #e0e9f4;
    --arrow: #286ea0;
    }
    /* --- Header Responsive --- */
    header {
    background: var(--step-alt);
    color: var(--accent);
    padding: 1rem 2vw;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border);
    flex-wrap: wrap;
    gap: 0.8em;
    }
    .icon-title {
    display: flex;
    align-items: center;
    gap: 0.75em;
    font-size: 1.25em;
    font-weight: bold;
    }
    header img {
    width: 32px; height: 32px;
    border-radius: 8px;
    box-shadow: 0 1px 4px #0002;
    flex-shrink: 0;
    }
    nav {
    display: flex;
    gap: 1.3em;
    flex-wrap: wrap;
    align-items: center;
    font-size: 1em;
    }
    nav a {
    color: var(--accent);
    text-decoration: none;
    font-weight: 500;
    transition: color .2s;
    padding: 0.3em 0.5em;
    border-radius: 5px;
    }
    nav a:hover { background: var(--step-bg); }
    .theme-toggle {
    display: flex;
    align-items: center;
    gap: .5em;
    cursor: pointer;
    font-size: 1rem;
    color: var(--fg);
    background: none;
    border: 1px solid var(--border);
    border-radius: 1em;
    padding: .3em 1em;
    transition: background .2s, color .2s, border .2s;
    margin-left: auto;
    }
    @media (max-width: 700px) {
    header {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.7em;
    padding: 0.8em 3vw 0.8em 3vw;
    position: relative; /* Added */
    }
    nav {
    gap: 0.7em;
    margin-top: 0.3em;
    font-size: 1em;
    width: 100%;
    flex-wrap: wrap;
    }
    .theme-toggle {
    position: absolute;  /* Added */
    top: 0.7em;           /* Added */
    right: 1em;           /* Added */
    margin-left: 0;
    margin-top: 0;
    }
    .icon-title {
    font-size: 1.05em;
    gap: 0.5em;
    }
    }
    @media (max-width: 430px) {
    header { padding: 0.5em 1vw; }
    .icon-title { font-size: 1em;}
    nav { font-size: 0.95em;}
    .theme-toggle { font-size: 0.98em; padding: .3em 0.8em; }
    }
    main {
    max-width: 900px;
    margin: 2rem auto;
    background: var(--step-bg);
    border-radius: 12px;
    box-shadow: 0 2px 20px #0001;
    padding: 2rem 2vw;
    }
    h1, h2, h3 {
    color: var(--accent);
    font-weight: 700;
    }
    .section { margin-bottom: 2.5rem; }
    .step-flow {
    display: flex;
    flex-direction: column;
    gap: 0;
    margin: 2em 0 2em 0;
    }
    .step {
    display: flex;
    align-items: flex-start;
    gap: 0.9em;
    background: var(--step-alt);
    border-radius: 8px;
    margin-bottom: 0;
    margin-top: 0;
    position: relative;
    border-left: 6px solid var(--accent);
    padding: 1.2em 1.2em 1.2em 2.3em;
    box-shadow: 0 2px 9px #0001;
    min-height: 44px;
    font-size: 1.04em;
    }
    .step-number {
    font-size: 1.6em;
    font-weight: 700;
    color: var(--accent);
    min-width: 2.2em;
    text-align: center;
    background: var(--step-bg);
    border-radius: 50%;
    border: 2px solid var(--accent);
    box-shadow: 0 1px 7px #0002;
    height: 2.2em;
    display: flex;
    align-items: center;
    justify-content: center;
    position: absolute;
    left: -1.4em;
    top: 1.1em;
    }
    .arrow {
    margin: 0 auto;
    color: var(--arrow);
    text-align: center;
    font-size: 2.3em;
    font-weight: bold;
    line-height: 1;
    padding: 0.13em 0 0.13em 0;
    width: 100%;
    user-select: none;
    background: none;
    border: none;
    outline: none;
    letter-spacing: 0.05em;
    }
    .note-block {
    background: var(--note-bg);
    color: var(--fg);
    border-radius: 8px;
    border-left: 4px solid var(--accent);
    padding: 1em 1.3em;
    margin: 1.5em 0 1.5em 0;
    font-family: system-ui,sans-serif;
    font-size: 1.08em;
    line-height: 1.7;
    }
    .input-box, .output-box {
    background: var(--input-bg);
    color: #cfe6ff;
    border-radius: 5px;
    font-family: 'Fira Mono', 'Consolas', monospace;
    font-size: 1em;
    padding: 1em 1.1em;
    margin-top: 1em;
    margin-bottom: 0.4em;
    white-space: pre-wrap;
    box-shadow: 0 2px 7px #0002;
    border-left: 4px solid var(--accent);
    }
    .output-box {
    background: var(--output-bg);
    color: #b8e7ff;
    border-left: 4px solid var(--arrow);
    }
    .light .input-box { background: var(--input-bg); color: #18436b; }
    .light .output-box { background: var(--output-bg); color: #18436b; }
    .output-link {
    display: inline-block;
    background: var(--accent);
    color: #fff;
    border-radius: 6px;
    padding: .4em 1.1em;
    text-decoration: none;
    font-weight: 600;
    margin-top: 1em;
    transition: background .13s;
    }
    .output-link:hover {
    background: #205d7a;
    }
    @media (max-width: 750px) {
    main { padding: 1rem 0.5rem; }
    .step { padding-left: 2.7em; }
    .step-number { left: -1.3em; }
    }
    @media (max-width: 500px) {
    .step { padding-left: 2.6em; }
    .step-number { left: -1.1em; top: 0.8em; }
    }