:root {
    --bg: #f5f5fa; --panel: #fff; --text: #1f2937; --muted: #6b7280; --border: #d1d5db;
    --primary: #4f46e5; --good: #059669; --bad: #dc2626;
    color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
    :root { --bg: #111827; --panel: #1f2937; --text: #f3f4f6; --muted: #9ca3af; --border: #374151; --primary: #818cf8; }
}
* { box-sizing: border-box; }
body { margin: 0; font: 17px/1.5 system-ui, sans-serif; background: var(--bg); color: var(--text); }
header { display: flex; justify-content: space-between; align-items: center; padding: .6rem 1rem; background: var(--primary); color: #fff; }
header a, header .link { color: #fff; }
.brand { font-weight: 700; text-decoration: none; font-size: 1.15rem; }
main { max-width: 640px; margin: 0 auto; padding: 1rem; }
h1, h2 { margin: 0 0 .8rem; line-height: 1.2; }
.title { font-size: 1.3rem; }
.panel { background: var(--panel); border-radius: 12px; padding: 1rem; margin-bottom: 1rem; box-shadow: 0 1px 3px #0002; }
.narrow { max-width: 360px; margin: 2rem auto; }
label { display: block; margin-bottom: .8rem; }
input:not([type=checkbox], [type=radio]), select, textarea {
    display: block; width: 100%; margin-top: .25rem; padding: .6rem; font: inherit;
    border: 1px solid var(--border); border-radius: 8px; background: var(--bg); color: var(--text);
}
textarea { font-family: ui-monospace, monospace; font-size: 15px; }
fieldset { border: 0; padding: 0; margin: 0 0 1rem; }
legend { font-weight: 600; margin-bottom: .3rem; }
.check { display: flex; gap: .6rem; align-items: center; margin: 0; padding: .4rem 0; cursor: pointer; flex: 1; }
.check input { width: 1.3rem; height: 1.3rem; accent-color: var(--primary); }
small, .hint { color: var(--muted); font-size: .85rem; }
button, .button {
    display: inline-block; padding: .65rem 1rem; font: inherit; border-radius: 8px; cursor: pointer; text-decoration: none;
    border: 1px solid var(--border); background: var(--panel); color: var(--text); text-align: center;
}
.primary { background: var(--primary); border-color: var(--primary); color: #fff; }
.good { background: var(--good); border-color: var(--good); color: #fff; }
.hot { border-color: #ea580c; color: #ea580c; }
.bad { background: var(--bad); border-color: var(--bad); color: #fff; }
.link { background: none; border: 0; padding: .3rem; text-decoration: underline; color: var(--muted); }
.danger { color: var(--bad); }
.row { display: flex; gap: .5rem; margin: .8rem 0; }
.row > * { flex: 1; }
.row:has(.hot) { flex-wrap: wrap; }
.row input { margin: 0; }
.lessons { list-style: none; padding: 0; margin: 0 0 .8rem; }
.lessons li { display: flex; align-items: center; gap: .4rem; border-bottom: 1px solid var(--border); padding: .3rem 0; }
.lessons .button { padding: .45rem .7rem; }
.flash { background: var(--good); color: #fff; padding: .6rem 1rem; border-radius: 8px; }
.error { color: var(--bad); }
.progress { text-align: center; color: var(--muted); margin: 0 0 .5rem; }

/* Flip card */
.card { perspective: 1000px; height: 220px; cursor: pointer; user-select: none; }
.inner { position: relative; height: 100%; transition: transform .4s; transform-style: preserve-3d; }
.card.flipped .inner { transform: rotateY(180deg); }
.face {
    position: absolute; inset: 0; display: flex; align-items: center; justify-content: center; padding: 1rem;
    border-radius: 16px; backface-visibility: hidden; font-size: 1.7rem; font-weight: 600; text-align: center;
    background: var(--panel); box-shadow: 0 4px 14px #0003; overflow-wrap: anywhere;
}
.back { transform: rotateY(180deg); background: var(--primary); color: #fff; }
.feedback { text-align: center; min-height: 1.5em; font-weight: 600; margin: .8rem 0 0; }
.feedback.good { color: var(--good); }
.feedback.bad { color: var(--bad); }
#mistakes li { padding: .2rem 0; }
table { width: 100%; border-collapse: collapse; margin-bottom: 1rem; }
th, td { text-align: left; padding: .4rem .3rem; border-bottom: 1px solid var(--border); vertical-align: top; }
th.day { padding-top: 1rem; color: var(--primary); }
td:first-child { white-space: nowrap; }
summary { cursor: pointer; color: var(--primary); }
details .row { min-width: 220px; }
[hidden] { display: none !important; }