:root {
  /* ── Όλα τα χρώματα εδώ. Σμαραγδί: ξεχωρίζει από το μωβ των Γ΄
        και το μπλε των Φυσικών. Η κάθε ενότητα έχει δικό της --c. ── */
  --bg: #f2faf7;
  --card: #ffffff;
  --ink: #17312c;
  --muted: #56706a;
  --line: #d9ece6;
  --primary: #0d8469;
  --good: #1fae6b;
  --bad: #ec4b5b;
  --warn: #f59e0b;
  --c: var(--primary);
  --c-soft: var(--c-soft-l, #e0f4ee);
  --good-soft: #dcf7e9; --good-ink: #127a4a;
  --bad-soft: #ffe3e6;  --bad-ink: #b3263a;
  --hl: #fff1a8;
  --hook-bg: #fff8e6; --hook-line: #f7c948;
  --ex-bg: #f0fbf5; --ex-ink: #15935a;
  --star-bg: #fff6d8;
  --topbar: rgba(255, 255, 255, .92);
  --hero: linear-gradient(135deg, #0d8469, #2aa9a0);
  --toast: #17312c;
  --w-paper: #ffffff; --w-grid: #9aa0bd; --w-soft: #f3f5ff; --w-blue: #cfd8ff; --w-orange: #ffe0c7;
  --radius: 18px;
  --shadow: 0 6px 20px rgba(20, 90, 75, .10);
  --font: "Segoe UI", system-ui, -apple-system, Roboto, "Noto Sans", "Helvetica Neue", Arial, sans-serif;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #121a19; --card: #1c2826; --ink: #e8f3f0; --muted: #a3b8b3; --line: #2e3f3c;
    --c-soft: color-mix(in srgb, var(--c) 26%, #1c2826);
    --good-soft: #173a2a; --good-ink: #7fe0ae; --bad-soft: #45222a; --bad-ink: #ff9aa6;
    --hl: #5a4a10; --hook-bg: #2c2717; --hook-line: #8a7320; --ex-bg: #16302a; --ex-ink: #6fd6a8;
    --star-bg: #3a3317; --topbar: rgba(22, 32, 30, .92); --hero: linear-gradient(135deg, #0b6f59, #1d8a83);
    --w-paper: #22302d; --w-grid: #6f8680; --w-soft: #1f2c2a; --w-blue: #2c3a66; --w-orange: #5a3a22;
  --toast: #0d8469; --shadow: 0 6px 20px rgba(0, 0, 0, .35);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #121a19; --card: #1c2826; --ink: #e8f3f0; --muted: #a3b8b3; --line: #2e3f3c;
  --c-soft: color-mix(in srgb, var(--c) 26%, #1c2826);
  --good-soft: #173a2a; --good-ink: #7fe0ae; --bad-soft: #45222a; --bad-ink: #ff9aa6;
  --hl: #5a4a10; --hook-bg: #2c2717; --hook-line: #8a7320; --ex-bg: #16302a; --ex-ink: #6fd6a8;
  --star-bg: #3a3317; --topbar: rgba(22, 32, 30, .92); --hero: linear-gradient(135deg, #0b6f59, #1d8a83);
  --w-paper: #22302d; --w-grid: #6f8680; --w-soft: #1f2c2a; --w-blue: #2c3a66; --w-orange: #5a3a22;
  --toast: #0d8469; --shadow: 0 6px 20px rgba(0, 0, 0, .35);
  color-scheme: dark;
}


* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: var(--font);
  font-size: 17px;
  line-height: 1.5;
  color: var(--ink);
  background: var(--bg);
  padding-bottom: env(safe-area-inset-bottom, 0px);
}
img, svg { max-width: 100%; }
[hidden] { display: none !important; }
button { font: inherit; color: inherit; }
a { color: var(--primary); }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 20;
  display: flex; align-items: center; gap: 8px;
  padding: calc(8px + env(safe-area-inset-top, 0px)) 12px 8px;
  background: var(--topbar);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 8px; text-decoration: none; color: var(--ink); font-size: 18px; }
.brand-owl { font-size: 26px; }
.brand b { color: var(--primary); }
.topbar-right { margin-left: auto; display: flex; align-items: center; gap: 6px; }
.star-count { font-weight: 700; background: var(--star-bg); border-radius: 999px; padding: 4px 10px; font-size: 15px; }
.icon-btn {
  border: 0; background: transparent; font-size: 22px; min-width: 40px; height: 40px;
  border-radius: 12px; cursor: pointer; display: inline-grid; place-items: center;
}
.icon-btn:hover { background: var(--c-soft); }

main { max-width: 900px; margin: 0 auto; padding: 16px 16px 90px; outline: none; }

/* ---------- common ---------- */
h1, h2, h3 { line-height: 1.25; margin: 0 0 .5em; }
h1 { font-size: 26px; }
h2 { font-size: 21px; }
h3 { font-size: 18px; }
.muted { color: var(--muted); }
.card {
  background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 16px; margin: 0 0 16px;
}
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  border: 0; border-radius: 14px; padding: 12px 18px; min-height: 46px;
  background: var(--c); color: #fff; font-weight: 700; font-size: 17px;
  cursor: pointer; text-decoration: none; box-shadow: 0 3px 0 rgba(0,0,0,.18);
  transition: transform .08s;
}
.btn:active { transform: translateY(2px); box-shadow: 0 1px 0 rgba(0,0,0,.18); }
.btn.secondary { background: var(--c-soft); color: var(--ink); box-shadow: 0 3px 0 rgba(0,0,0,.08); }
.btn.small { padding: 6px 12px; min-height: 36px; font-size: 15px; }
.btn.wide { width: 100%; }
.btn:disabled { opacity: .5; cursor: default; }
.row { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
.center { text-align: center; }
.spacer { height: 12px; }

/* ---------- home ---------- */
.hero {
  background: var(--hero);
  color: #fff; border-radius: 24px; padding: 20px; margin-bottom: 18px;
  display: flex; gap: 14px; align-items: center; box-shadow: var(--shadow);
}
.hero h1 { margin: 0 0 4px; font-size: 24px; }
.hero p { margin: 0; opacity: .95; }
.hero .owl { font-size: 58px; line-height: 1; animation: bob 3s ease-in-out infinite; }
@keyframes bob { 50% { transform: translateY(-6px) rotate(-4deg); } }
.name-input { border: 0; border-radius: 10px; padding: 6px 10px; font: inherit; width: 150px; margin-top: 8px; }

.unit-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 14px; }
.unit-card {
  display: block; text-decoration: none; color: var(--ink);
  background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 16px; border-top: 8px solid var(--c); position: relative; overflow: hidden;
}
.unit-card .u-emoji { font-size: 36px; position: absolute; right: 12px; top: 10px; opacity: .9; }
.unit-card .u-num { font-weight: 800; color: var(--c); font-size: 14px; text-transform: uppercase; letter-spacing: .04em; }
.unit-card h3 { margin: 4px 50px 6px 0; font-size: 19px; }
.unit-card .u-meta { font-size: 14px; color: var(--muted); }
.meter { height: 10px; border-radius: 99px; background: var(--line); overflow: hidden; margin-top: 10px; }
.meter > span { display: block; height: 100%; background: var(--c); border-radius: 99px; transition: width .4s; }

.lesson-list { display: grid; gap: 10px; }
.lesson-item {
  display: flex; align-items: center; gap: 12px; text-decoration: none; color: var(--ink);
  background: var(--card); border-radius: 16px; padding: 12px 14px; box-shadow: var(--shadow);
  border-left: 6px solid var(--c);
}
.lesson-item .l-num {
  flex: 0 0 auto; width: 44px; height: 44px; border-radius: 12px; background: var(--c-soft);
  display: grid; place-items: center; font-weight: 800; color: var(--c);
}
.lesson-item .l-title { font-weight: 650; }
.lesson-item .l-emoji { font-size: 24px; margin-left: auto; }
.lesson-item.review { border-left-style: dashed; }
.stars { letter-spacing: 1px; font-size: 14px; white-space: nowrap; }
.stars .off { filter: grayscale(1); opacity: .3; }

.unit-head {
  border-radius: 22px; padding: 18px; color: #fff; margin-bottom: 16px;
  background: var(--c); box-shadow: var(--shadow);
}
.unit-head h1 { margin: 0; font-size: 23px; }
.unit-head p { margin: 4px 0 0; opacity: .95; }

/* ---------- lesson ---------- */
.lesson-head { display: flex; gap: 12px; align-items: center; margin-bottom: 14px; }
.lesson-head .big-emoji { font-size: 46px; }
.lesson-head .kicker { color: var(--c); font-weight: 800; font-size: 14px; }
.lesson-head h1 { margin: 0; font-size: 23px; }

.tabs {
  position: sticky; top: calc(57px + env(safe-area-inset-top, 0px)); z-index: 10;
  display: flex; gap: 6px; overflow-x: auto; padding: 6px 0 10px; background: var(--bg);
  scrollbar-width: none;
}
.tabs::-webkit-scrollbar { display: none; }
.tab {
  flex: 0 0 auto; border: 0; border-radius: 999px; padding: 8px 14px; background: var(--card);
  box-shadow: var(--shadow); cursor: pointer; font-weight: 650; font-size: 15px;
}
.tab.active { background: var(--c); color: #fff; }

.section-title { display: flex; align-items: center; gap: 8px; font-size: 20px; margin: 6px 0 12px; }
.section-title .ico { font-size: 26px; }

.hook { background: var(--hook-bg); border: 2px dashed var(--hook-line); }
.owl-say { display: flex; gap: 10px; align-items: flex-start; }
.owl-say .owl { font-size: 34px; line-height: 1; }
.owl-say .bubble {
  background: var(--card); border-radius: 16px; padding: 10px 14px; box-shadow: var(--shadow); position: relative; flex: 1;
}
.keyidea { border-left: 6px solid var(--c); }
.keyidea h3 { color: var(--c); }
.keyidea p:last-child, .keyidea ul:last-child { margin-bottom: 0; }
.rule {
  background: var(--c-soft); border-radius: 12px; padding: 10px 12px; margin: 10px 0; font-weight: 600;
}
.example { background: var(--ex-bg); border-left: 6px solid var(--good); }
.example h3 { color: var(--ex-ink); }
.bookref { font-size: 14px; }
.hl { background: var(--hl); border-radius: 4px; padding: 0 3px; }
.big { font-size: 1.3em; font-weight: 700; }
.mono { font-variant-numeric: tabular-nums; }
.def { font-weight: 700; color: var(--c); }
table.simple { border-collapse: collapse; margin: 8px 0; }
table.simple td, table.simple th { border: 1px solid var(--line); padding: 6px 10px; text-align: center; }
table.simple th { background: var(--c-soft); }
.scroll-x { overflow-x: auto; max-width: 100%; }

/* fractions */
.frac { display: inline-flex; flex-direction: column; align-items: center; vertical-align: middle; line-height: 1.1; margin: 0 2px; font-weight: 600; }
.frac > span:first-child { border-bottom: 2px solid currentColor; padding: 0 3px; }
.frac > span { padding: 0 3px; }
.mixed { display: inline-flex; align-items: center; gap: 1px; }

/* ---------- widgets ---------- */
.widget { border: 3px solid var(--c-soft); }
.widget .w-title { font-weight: 800; margin-bottom: 6px; }
.widget .w-help { color: var(--muted); font-size: 15px; margin: 0 0 10px; }
.widget svg { display: block; margin: 0 auto; touch-action: none; user-select: none; }
/* Κείμενο SVG χωρίς χρώμα = μαύρο από προεπιλογή· εδώ ακολουθεί το θέμα. */
.widget svg text:not([fill]) { fill: var(--ink); }
.w-out { background: var(--c-soft); border-radius: 12px; padding: 10px 12px; margin-top: 10px; min-height: 44px; }
.w-out.good { background: var(--good-soft); }
.w-out.bad { background: var(--bad-soft); }
.ctrl { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 12px; margin: 8px 0; }
.ctrl label { font-weight: 600; font-size: 15px; }
.stepper { display: inline-flex; align-items: center; background: var(--c-soft); border-radius: 12px; overflow: hidden; }
.stepper button { border: 0; background: transparent; width: 40px; height: 40px; font-size: 22px; font-weight: 800; cursor: pointer; color: var(--c); }
.stepper button:active { background: rgba(0,0,0,.06); }
.stepper .val { min-width: 42px; text-align: center; font-weight: 800; font-variant-numeric: tabular-nums; }
input[type=range] { width: 100%; max-width: 360px; accent-color: var(--c); height: 30px; }
.num-in, .text-in {
  font: inherit; font-size: 18px; padding: 8px 10px; border: 2px solid var(--line); border-radius: 12px;
  width: 140px; background: var(--card); color: var(--ink);
}
.num-in:focus, .text-in:focus { outline: none; border-color: var(--c); }
.seg { display: inline-flex; background: var(--c-soft); border-radius: 12px; padding: 3px; flex-wrap: wrap; }
.seg button { border: 0; background: transparent; padding: 7px 12px; border-radius: 10px; cursor: pointer; font-weight: 650; font-size: 15px; }
.seg button.on { background: var(--c); color: #fff; }
.chip { display: inline-block; padding: 4px 10px; border-radius: 999px; background: var(--c-soft); font-weight: 650; font-size: 15px; }
.chip.good { background: var(--good-soft); color: var(--good-ink); }
.chip.bad { background: var(--bad-soft); color: var(--bad-ink); }

.pv-table { border-collapse: separate; border-spacing: 3px; margin: 0 auto; font-variant-numeric: tabular-nums; }
.pv-table th { font-size: 12px; background: var(--c-soft); border-radius: 8px; padding: 4px 3px; font-weight: 700; min-width: 34px; }
.pv-table th.grp { font-size: 12px; background: transparent; color: var(--muted); }
.pv-table td { text-align: center; }
.pv-table .digit {
  font-size: 22px; font-weight: 800; width: 34px; height: 44px; border-radius: 10px; border: 2px solid var(--line);
  display: grid; place-items: center; background: var(--card); cursor: pointer; user-select: none;
}
.pv-table .digit.sel { border-color: var(--c); background: var(--c-soft); }
.pv-table .comma { font-size: 28px; font-weight: 900; padding: 0; min-width: 8px; color: var(--bad); }

.col-op { font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace; font-size: 24px; display: inline-grid; gap: 0; margin: 0 auto; }
.col-op .r { display: flex; justify-content: flex-end; }
.col-op .c { width: 1.1em; text-align: center; }
.col-op .carry { font-size: 14px; color: var(--bad); height: 18px; }
.col-op .line { border-top: 3px solid var(--ink); }
.col-op .hlc { background: var(--hl); border-radius: 4px; }

.grid-100 { display: grid; grid-template-columns: repeat(10, 1fr); gap: 3px; max-width: 420px; margin: 0 auto; }
.grid-100 > div {
  aspect-ratio: 1; display: grid; place-items: center; border-radius: 6px; background: var(--card);
  border: 1px solid var(--line); font-size: 13px; font-weight: 700; cursor: pointer; user-select: none;
}

.match-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.match-card {
  border: 2px solid var(--line); background: var(--card); border-radius: 14px; padding: 10px; min-height: 56px;
  display: grid; place-items: center; font-weight: 700; font-size: 18px; cursor: pointer;
}
.match-card.sel { border-color: var(--c); background: var(--c-soft); }
.match-card.done { border-color: var(--good); background: var(--good-soft); cursor: default; opacity: .75; }
.match-card.shake { animation: shake .35s; }
@keyframes shake { 25% { transform: translateX(-5px); } 75% { transform: translateX(5px); } }

/* ---------- quiz ---------- */
.quiz-top { display: flex; align-items: center; gap: 10px; margin-bottom: 12px; }
.progress { flex: 1; height: 14px; background: var(--line); border-radius: 99px; overflow: hidden; }
.progress > span { display: block; height: 100%; background: var(--c); transition: width .3s; }
.q-card { font-size: 19px; }
.q-card .q-text { font-weight: 650; margin-bottom: 14px; }
.options { display: grid; gap: 10px; }
.opt {
  text-align: left; border: 2px solid var(--line); background: var(--card); border-radius: 14px; padding: 12px 14px;
  font-size: 18px; cursor: pointer; min-height: 52px; display: flex; align-items: center; gap: 10px;
}
.opt .letter { flex: 0 0 auto; width: 30px; height: 30px; border-radius: 9px; background: var(--c-soft); display: grid; place-items: center; font-weight: 800; color: var(--c); }
.opt:hover:not(:disabled) { border-color: var(--c); }
.opt.correct { border-color: var(--good); background: var(--good-soft); }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.opt:disabled { cursor: default; }
.tf-row { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.tf-row .opt { justify-content: center; font-weight: 800; }
.feedback { margin-top: 14px; border-radius: 14px; padding: 12px 14px; font-size: 17px; }
.feedback.good { background: var(--good-soft); }
.feedback.bad { background: var(--bad-soft); }
.feedback b { display: block; font-size: 19px; margin-bottom: 2px; }
.input-row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }
.input-row .num-in { width: 170px; }
.hint-line { font-size: 14px; color: var(--muted); margin-top: 6px; }
.result { text-align: center; }
.result .big-stars { font-size: 50px; letter-spacing: 6px; margin: 10px 0; }
.result .big-stars .off { filter: grayscale(1); opacity: .25; }
.result .score { font-size: 28px; font-weight: 800; }

/* install bar */
.install-bar {
  position: fixed; left: 12px; right: 12px; bottom: calc(12px + env(safe-area-inset-bottom, 0px)); z-index: 30;
  background: var(--toast); color: #fff; border-radius: 16px; padding: 10px 12px;
  display: flex; align-items: center; gap: 10px; box-shadow: 0 10px 30px rgba(0,0,0,.25);
  max-width: 560px; margin: 0 auto;
}
.install-bar span { flex: 1; font-size: 15px; }
.install-bar .icon-btn { color: #fff; }

#confetti { position: fixed; inset: 0; pointer-events: none; z-index: 50; }

.footer { text-align: center; color: var(--muted); font-size: 13px; margin-top: 30px; }

@media (max-width: 520px) {
  body { font-size: 16px; }
  main { padding: 12px 12px 90px; }
  h1 { font-size: 22px; }
  .hero { padding: 16px; }
  .hero .owl { font-size: 46px; }
  .q-card { font-size: 18px; }
  .opt { font-size: 17px; }
  .pv-table { border-spacing: 2px; }
  .pv-table .digit { width: 26px; height: 40px; font-size: 19px; }
  .pv-table th { min-width: 26px; font-size: 10px; padding: 4px 1px; }
  .pv-table th.grp { font-size: 10px; }
  .col-op { font-size: 21px; }
}
@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
}