:root {
    --bg: #111318;
    --panel: #1a1d24;
    --panel-soft: #20242d;
    --border: #343a48;
    --text: #edf0f5;
    --muted: #9ba3b3;
    --purple: #b98be8;
    --green: #78c985;
    --danger: #ef8c8c;
    --font-serif: "Noto Serif SC", serif;
    --font-sans: "Noto Sans SC", sans-serif;
}

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

body {
    min-height: 100vh;
    background:
        radial-gradient(circle at 16% 0, rgba(155, 107, 201, 0.13), transparent 34rem),
        radial-gradient(circle at 88% 88%, rgba(95, 173, 106, 0.08), transparent 30rem),
        var(--bg);
    color: var(--text);
    font-family: var(--font-sans);
}

.convert-shell { width: min(860px, calc(100% - 2rem)); margin: 0 auto; padding: 2rem 0 3rem; }
.convert-nav { display: flex; align-items: center; justify-content: space-between; margin-bottom: 3.5rem; color: var(--muted); font-size: 0.8rem; }
.convert-nav a { color: var(--muted); text-decoration: none; }
.convert-nav a:hover { color: var(--purple); }
.convert-nav span { padding: 0.3rem 0.6rem; border: 1px solid var(--border); border-radius: 999px; }

.convert-header { margin-bottom: 1.5rem; text-align: center; }
.convert-header p { color: var(--purple); font-size: 0.72rem; font-weight: 700; letter-spacing: 0.28em; }
.convert-header h1 { margin: 0.55rem 0; font: 700 clamp(2.2rem, 7vw, 3.8rem) var(--font-serif); letter-spacing: 0.12em; }
.convert-header span { color: var(--muted); font-size: 0.88rem; line-height: 1.7; }

.convert-panel { padding: clamp(1.1rem, 4vw, 2rem); border: 1px solid var(--border); border-radius: 14px; background: rgba(26, 29, 36, 0.96); box-shadow: 0 20px 55px rgba(0, 0, 0, 0.22); }
.panel-heading { display: flex; align-items: flex-start; justify-content: space-between; gap: 1rem; padding-bottom: 1rem; border-bottom: 1px solid var(--border); }
.panel-heading h2 { font: 600 1.2rem var(--font-serif); }
.panel-heading > strong { color: var(--purple); font-size: 0.78rem; letter-spacing: 0.08em; }

.privacy-note { display: grid; gap: 0.35rem; margin: 1.2rem 0; padding: 0.9rem 1rem; border-left: 3px solid var(--green); background: var(--panel-soft); }
.privacy-note strong { color: var(--green); font-size: 0.82rem; }
.privacy-note span { color: var(--muted); font-size: 0.74rem; line-height: 1.6; }

.form-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; }
.field { display: grid; gap: 0.45rem; color: var(--muted); font-size: 0.76rem; }
.field select, .field input { width: 100%; min-height: 2.8rem; padding: 0.68rem 0.75rem; border: 1px solid var(--border); border-radius: 8px; outline: none; background: #12141a; color: var(--text); font: 0.84rem var(--font-sans); }
.field select:focus, .field input:focus { border-color: rgba(185, 139, 232, 0.7); }

.file-drop { display: grid; gap: 0.45rem; margin: 1rem 0; padding: 1.4rem 1rem; border: 1px dashed #4c5363; border-radius: 10px; cursor: pointer; background: rgba(17, 19, 24, 0.55); text-align: center; }
.file-drop:hover { border-color: rgba(185, 139, 232, 0.75); background: rgba(155, 107, 201, 0.06); }
.file-drop strong { color: var(--purple); font: 600 0.95rem var(--font-serif); overflow-wrap: anywhere; }

.btn-convert { width: 100%; min-height: 3rem; border: 1px solid rgba(185, 139, 232, 0.58); border-radius: 8px; cursor: pointer; background: rgba(155, 107, 201, 0.2); color: #d7b3fa; font: 600 0.9rem var(--font-sans); transition: transform 0.15s, background 0.15s; }
.btn-convert:hover:not(:disabled) { transform: translateY(-1px); background: rgba(155, 107, 201, 0.28); }
.btn-convert:disabled { cursor: wait; opacity: 0.55; }
.convert-message { min-height: 1.5rem; margin-top: 0.8rem; color: var(--muted); font-size: 0.74rem; text-align: center; line-height: 1.6; }
.convert-message.is-error { color: var(--danger); }
.convert-message.is-success { color: var(--green); }

.convert-steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0.8rem; margin-top: 1rem; }
.convert-steps article { padding: 1rem; border: 1px solid var(--border); border-radius: 10px; background: rgba(26, 29, 36, 0.76); }
.convert-steps span { color: var(--purple); font-size: 0.68rem; }
.convert-steps strong { display: block; margin: 0.35rem 0; font: 600 0.9rem var(--font-serif); }
.convert-steps p { color: var(--muted); font-size: 0.7rem; line-height: 1.6; }
.app-footer { margin-top: 2rem; color: var(--muted); font-size: 0.72rem; text-align: center; }
.app-footer a { color: var(--purple); }

@media (max-width: 620px) {
    .convert-shell { width: min(100% - 1rem, 860px); padding-top: 1rem; }
    .convert-nav { margin-bottom: 2.5rem; }
    .form-grid, .convert-steps { grid-template-columns: 1fr; }
    .convert-header span { display: block; padding: 0 0.75rem; }
}