:root {
    --accent: #1f5fd1;
    --accent-soft: #e5edfb;
    --bg: #f4f6fa;
    --surface: #ffffff;
    --text: #172033;
    --muted: #5d6779;
    --border: #dde3ec;
    --positive: #11804a;
    --negative: #c62f2f;
    --warn-bg: #fff4d6;
    --warn-text: #7a5600;
    --grid: #e6eaf1;
    --radius: 14px;
    --shadow: 0 6px 24px rgba(23, 32, 51, .06);
}

@media (prefers-color-scheme: dark) {
    :root {
        --accent: #6b9dff;
        --accent-soft: #1c2a47;
        --bg: #0f1420;
        --surface: #171e2d;
        --text: #e7ecf5;
        --muted: #9aa5b8;
        --border: #2a3448;
        --positive: #4cc98a;
        --negative: #ff7474;
        --warn-bg: #3a2f10;
        --warn-text: #f3cf73;
        --grid: #263044;
        --shadow: 0 6px 24px rgba(0, 0, 0, .3);
    }
}

* { box-sizing: border-box; }
body {
    margin: 0;
    font-family: "Inter", system-ui, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.5;
}
a { color: var(--accent); }
.wrap { width: min(960px, 100% - 2rem); margin-inline: auto; }

/* Barra superiore */
.topbar {
    position: sticky; top: 0; z-index: 10;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
}
.topbar-inner { display: flex; justify-content: space-between; align-items: center; padding: .8rem 0; gap: 1rem; }
.brand { font-weight: 700; text-decoration: none; color: var(--text); display: flex; align-items: center; gap: .5rem; }
.brand-mark { background: var(--accent); color: #fff; border-radius: 8px; padding: .15rem .4rem; font-size: .85rem; }
.topbar nav { display: flex; gap: 1rem; }
.topbar nav a { text-decoration: none; color: var(--muted); font-weight: 500; }
.topbar nav a:hover { color: var(--accent); }

main { padding: 1.5rem 0 2rem; display: grid; gap: 1.25rem; }
.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 1.5rem;
}
h1, h2 { margin: 0 0 .25rem; line-height: 1.2; }
h1 { font-size: 1.7rem; }
h2 { font-size: 1.3rem; }
.lead { margin: 0 0 1.25rem; color: var(--muted); }
.muted { color: var(--muted); }
.small { font-size: .9rem; }

/* Form */
.form-grid { display: grid; grid-template-columns: 1fr 1.4fr auto 1.4fr; gap: .75rem; align-items: end; }
.field { display: grid; gap: .3rem; font-size: .9rem; color: var(--muted); font-weight: 500; }
.field input, .field select {
    font: inherit; font-size: 1.05rem; color: var(--text);
    background: var(--bg); border: 1px solid var(--border); border-radius: 10px;
    padding: .7rem .8rem; width: 100%;
}
.field input:focus, .field select:focus, button:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
.field input.invalid { border-color: var(--negative); }
.field-error { color: var(--negative); margin: .4rem 0 0; font-size: .9rem; }
.swap {
    font-size: 1.3rem; width: 48px; height: 48px; border-radius: 50%;
    border: 1px solid var(--border); background: var(--accent-soft); color: var(--accent);
    cursor: pointer; transition: transform .2s;
}
.swap:hover { transform: rotate(180deg); }

/* Risultato */
.result { margin: 1.5rem 0 1rem; }
.result-main { font-size: clamp(2rem, 6vw, 3rem); font-weight: 700; margin: 0; word-break: break-word; }
.result-rate { margin: .2rem 0 0; font-size: 1.05rem; }
.meta { display: flex; flex-wrap: wrap; gap: .5rem; }
.badge { background: var(--accent-soft); color: var(--accent); padding: .35rem .7rem; border-radius: 999px; font-size: .9rem; font-weight: 600; }
.badge-warn { background: var(--warn-bg); color: var(--warn-text); }
.alert { background: var(--warn-bg); color: var(--warn-text); padding: .8rem 1rem; border-radius: 10px; margin: 1rem 0 0; }
.loading .result-main { opacity: .45; }

/* Storico */
.section-head { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: .75rem; margin-bottom: 1rem; }
.periods { display: flex; gap: .3rem; background: var(--bg); padding: .25rem; border-radius: 10px; border: 1px solid var(--border); }
.periods button {
    font: inherit; font-weight: 600; border: 0; background: transparent; color: var(--muted);
    padding: .4rem .8rem; border-radius: 8px; cursor: pointer;
}
.periods button.active { background: var(--accent); color: #fff; }
.chart-box { position: relative; height: 280px; }
#chart { width: 100%; height: 100%; display: block; }
.chart-status {
    position: absolute; inset: 0; display: grid; place-items: center;
    color: var(--muted); background: var(--surface); text-align: center; padding: 1rem;
}
.chart-status[hidden] { display: none; }
.chart-tooltip {
    position: absolute; pointer-events: none; background: var(--text); color: var(--surface);
    padding: .35rem .6rem; border-radius: 8px; font-size: .85rem; white-space: nowrap;
    transform: translate(-50%, -120%);
}
.stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: .75rem; margin: 1rem 0 0; }
.stats div { background: var(--bg); border-radius: 10px; padding: .7rem .9rem; }
.stats dt { color: var(--muted); font-size: .85rem; }
.stats dd { margin: 0; font-weight: 700; font-size: 1.1rem; }
.positive { color: var(--positive); }
.negative { color: var(--negative); }

/* Preferite */
.favorites { list-style: none; padding: 0; margin: .75rem 0 0; display: flex; flex-wrap: wrap; gap: .5rem; }
.favorites button {
    font: inherit; font-weight: 600; cursor: pointer;
    background: var(--accent-soft); color: var(--accent);
    border: 1px solid transparent; border-radius: 999px; padding: .45rem .9rem;
}
.favorites button:hover { border-color: var(--accent); }

.footer { border-top: 1px solid var(--border); padding: 1.5rem 0; color: var(--muted); font-size: .9rem; text-align: center; }
.footer p { margin: .25rem 0; }

@media (max-width: 720px) {
    .form-grid { grid-template-columns: 1fr auto 1fr; }
    .field-amount { grid-column: 1 / -1; }
    .topbar nav { display: none; }
    .stats { grid-template-columns: 1fr; }
    .card { padding: 1.1rem; }
    .chart-box { height: 230px; }
}