:root{
  --paper:#f5edd6;
  --ink:#2b2118;
  --terra:#d8552f;
  --terra-deep:#b03e1d;
  --teal:#1f6b63;
  --gold:#e8a83a;
  --line:#cdbf9a;
  --shadow:rgba(43,33,24,.18);
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:'Fraunces',Georgia,serif;
  background:var(--paper);
  color:var(--ink);
  min-height:100vh;
  background-image:
    radial-gradient(circle at 12% 18%, rgba(216,85,47,.06), transparent 28%),
    radial-gradient(circle at 88% 72%, rgba(31,107,99,.07), transparent 32%),
    repeating-linear-gradient(0deg, transparent, transparent 38px, rgba(205,191,154,.28) 38px, rgba(205,191,154,.28) 39px);
  overflow-x:hidden;
}
.grain{position:fixed;inset:0;pointer-events:none;opacity:.05;z-index:1;
  background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='100' height='100'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.9' numOctaves='2'/%3E%3C/filter%3E%3Crect width='100' height='100' filter='url(%23n)'/%3E%3C/svg%3E");}
.wrap{max-width:920px;margin:0 auto;padding:0 22px;position:relative;z-index:2}

/* Header */
header{padding:54px 0 24px;text-align:center;position:relative}
.kicker{font-family:'Space Mono',monospace;font-size:.72rem;letter-spacing:.34em;
  text-transform:uppercase;color:var(--terra-deep);margin-bottom:14px}
h1{font-size:clamp(3rem,11vw,6.2rem);font-weight:900;line-height:.86;letter-spacing:-.02em}
h1 .x{color:var(--terra);font-style:italic;display:inline-block;transform:rotate(-6deg)}
.sub{font-size:1.05rem;max-width:430px;margin:18px auto 0;color:#5b4a38;font-weight:400}

/* Tabs */
nav{display:flex;gap:8px;justify-content:center;margin:38px 0 30px;flex-wrap:wrap}
.tab{font-family:'Space Mono',monospace;font-size:.82rem;letter-spacing:.05em;
  text-transform:uppercase;padding:11px 22px;border:2px solid var(--ink);
  background:transparent;color:var(--ink);cursor:pointer;border-radius:40px;
  transition:all .18s ease;font-weight:700}
.tab:hover{transform:translateY(-2px)}
.tab.active{background:var(--ink);color:var(--paper);box-shadow:4px 4px 0 var(--terra)}

.panel{display:none;animation:rise .4s ease both}
.panel.show{display:block}
@keyframes rise{from{opacity:0;transform:translateY(14px)}to{opacity:1;transform:none}}

/* Learn */
.picker{display:flex;gap:8px;justify-content:center;flex-wrap:wrap;margin-bottom:28px}
.chip{width:48px;height:48px;border-radius:50%;border:2px solid var(--line);
  background:#fffdf6;font-family:'Space Mono',monospace;font-weight:700;font-size:1rem;
  cursor:pointer;color:var(--ink);transition:all .16s ease}
.chip:hover{border-color:var(--terra);transform:scale(1.08)}
.chip.sel{background:var(--terra);color:#fff;border-color:var(--terra-deep);
  box-shadow:0 6px 14px rgba(216,85,47,.4)}
.rows{display:grid;gap:10px;max-width:480px;margin:0 auto}
.row{display:flex;align-items:center;justify-content:space-between;
  background:#fffdf6;border:1.5px solid var(--line);border-radius:14px;
  padding:14px 22px;font-size:1.35rem;box-shadow:0 3px 0 var(--line);
  animation:slidein .35s ease both}
@keyframes slidein{from{opacity:0;transform:translateX(-16px)}to{opacity:1;transform:none}}
.row .eq{font-family:'Space Mono',monospace;color:#7a6850;font-size:1rem}
.row .ans{font-weight:900;color:var(--teal);font-size:1.6rem;min-width:54px;text-align:right}

/* Flashcards */
.stage{max-width:380px;margin:0 auto;text-align:center}
.card{perspective:1200px;height:280px;cursor:pointer;margin-bottom:24px}
.inner{position:relative;width:100%;height:100%;transition:transform .55s cubic-bezier(.4,.2,.2,1);
  transform-style:preserve-3d}
.card.flipped .inner{transform:rotateY(180deg)}
.face{position:absolute;inset:0;backface-visibility:hidden;border-radius:22px;
  display:flex;flex-direction:column;align-items:center;justify-content:center;
  border:2.5px solid var(--ink);box-shadow:8px 8px 0 var(--shadow)}
.front{background:#fffdf6}
.front .q{font-size:3.4rem;font-weight:900}
.front .hint{font-family:'Space Mono',monospace;font-size:.72rem;letter-spacing:.2em;
  text-transform:uppercase;color:#a08a6e;margin-top:14px}
.back{background:var(--teal);color:#fffdf6;transform:rotateY(180deg)}
.back .a{font-size:4.2rem;font-weight:900}
.deck-ctrl{display:flex;gap:10px;justify-content:center}
.btn{font-family:'Space Mono',monospace;font-weight:700;font-size:.82rem;
  text-transform:uppercase;letter-spacing:.06em;padding:13px 26px;border-radius:40px;
  border:2px solid var(--ink);background:var(--ink);color:var(--paper);cursor:pointer;
  transition:all .16s ease}
.btn:hover{transform:translateY(-2px);box-shadow:0 5px 0 var(--terra)}
.btn.ghost{background:transparent;color:var(--ink)}
.btn.active-rand{background:var(--gold);color:var(--ink);box-shadow:0 5px 0 var(--terra-deep)}
.progress{font-family:'Space Mono',monospace;font-size:.8rem;color:#7a6850;margin-bottom:18px;letter-spacing:.1em}

/* Quiz */
.quiz{max-width:420px;margin:0 auto;text-align:center}
.scorebar{display:flex;justify-content:space-between;font-family:'Space Mono',monospace;
  font-size:.82rem;letter-spacing:.08em;margin-bottom:22px;color:#5b4a38}
.scorebar b{color:var(--terra-deep)}
.qbox{background:#fffdf6;border:2.5px solid var(--ink);border-radius:22px;padding:38px 24px;
  box-shadow:8px 8px 0 var(--shadow);margin-bottom:22px}
.qbox .prompt{font-size:3rem;font-weight:900;margin-bottom:8px}
.qbox .meta{font-family:'Space Mono',monospace;font-size:.72rem;letter-spacing:.2em;
  text-transform:uppercase;color:#a08a6e}
.opts{display:grid;grid-template-columns:1fr 1fr;gap:12px}
.opt{padding:20px;font-size:1.5rem;font-weight:900;border:2px solid var(--line);
  background:#fffdf6;border-radius:14px;cursor:pointer;transition:all .14s ease;color:var(--ink)}
.opt:hover{border-color:var(--terra);transform:translateY(-2px)}
.opt.right{background:var(--teal);color:#fff;border-color:var(--teal);animation:pop .3s}
.opt.wrong{background:var(--terra);color:#fff;border-color:var(--terra-deep);animation:shake .3s}
@keyframes pop{50%{transform:scale(1.06)}}
@keyframes shake{25%{transform:translateX(-6px)}75%{transform:translateX(6px)}}
.result{text-align:center;padding:30px 0}
.result .big{font-size:4.5rem;font-weight:900;color:var(--terra);line-height:1}
.result .label{font-family:'Space Mono',monospace;letter-spacing:.18em;text-transform:uppercase;
  font-size:.8rem;color:#7a6850;margin:10px 0 24px}
.streak{display:inline-block;font-family:'Space Mono',monospace;font-size:.78rem;
  background:var(--gold);color:var(--ink);padding:4px 12px;border-radius:20px;font-weight:700;
  border:1.5px solid var(--ink)}

footer{text-align:center;padding:50px 0 40px;font-family:'Space Mono',monospace;
  font-size:.72rem;letter-spacing:.14em;color:#a08a6e;text-transform:uppercase}
.opts.locked .opt{pointer-events:none;opacity:.55}
.opts.locked .opt.right,.opts.locked .opt.wrong{opacity:1}

/* Type It Quiz */
.typeit-wrap{max-width:420px;margin:0 auto;text-align:center}
.type-input-wrap{display:flex;gap:10px;justify-content:center;align-items:center;margin-bottom:16px}
.type-input{
  font-family:'Space Mono',monospace;font-size:2rem;font-weight:700;
  width:130px;padding:14px 16px;text-align:center;
  border:2.5px solid var(--ink);border-radius:14px;
  background:#fffdf6;color:var(--ink);
  outline:none;transition:border-color .16s,box-shadow .16s;
  -moz-appearance:textfield;
}
.type-input::-webkit-inner-spin-button,.type-input::-webkit-outer-spin-button{-webkit-appearance:none}
.type-input:focus{border-color:var(--teal);box-shadow:0 0 0 3px rgba(31,107,99,.18)}
.type-input.ti-right{border-color:var(--teal);background:#e6f4f2;color:var(--teal)}
.type-input.ti-wrong{border-color:var(--terra);background:#faeae5;color:var(--terra-deep);animation:shake .3s}
.type-input:disabled{opacity:1}
.type-feedback{min-height:32px;font-family:'Space Mono',monospace;font-size:.9rem;font-weight:700;letter-spacing:.06em}
.ti-ok{color:var(--teal)}
.ti-bad{color:var(--terra-deep)}
.ti-bad b{color:var(--ink)}

/* Mode switches (quiz / squares & cubes / fill blank) */
.modebar{display:flex;gap:8px;justify-content:center;flex-wrap:wrap;margin-bottom:26px}
.mode{font-family:'Space Mono',monospace;font-size:.75rem;font-weight:700;letter-spacing:.04em;
  padding:9px 16px;border:2px solid var(--line);background:#fffdf6;color:var(--ink);
  border-radius:30px;cursor:pointer;transition:all .16s ease}
.mode:hover{border-color:var(--terra)}
.mode.sel{background:var(--teal);color:#fff;border-color:var(--teal);box-shadow:0 4px 0 rgba(31,107,99,.35)}

/* Squares & Cubes */
.pow-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(150px,1fr));gap:12px}
.pow{display:flex;flex-direction:column;align-items:center;gap:4px;padding:16px 10px 12px;
  background:#fffdf6;border:1.5px solid var(--line);border-radius:14px;box-shadow:0 3px 0 var(--line);
  animation:slidein .35s ease both}
.pow .b{font-family:'Space Mono',monospace;font-weight:700;font-size:1rem;color:#7a6850}
.pow .b sup{font-size:.7em;color:var(--terra-deep)}
.pow .v{font-weight:900;font-size:1.9rem;color:var(--teal);line-height:1.1}
.pow .calc{font-family:'Space Mono',monospace;font-size:.68rem;color:#a08a6e;letter-spacing:.04em}
.pow.cube .v{color:var(--terra)}

/* Fill in the blank */
.fill-eq{display:flex;flex-wrap:wrap;justify-content:center;align-items:center;gap:10px 14px;
  font-size:2.6rem;font-weight:900;margin-bottom:12px}
.fill-eq .op{color:var(--terra);font-style:italic}
.fill-eq sup{font-size:.55em;color:var(--terra-deep)}
.blank-input{font-family:'Space Mono',monospace;font-size:1.8rem;font-weight:700;
  width:118px;padding:6px 8px;text-align:center;color:var(--ink);
  border:none;border-bottom:4px solid var(--ink);border-radius:8px 8px 0 0;
  background:rgba(232,168,58,.22);outline:none;transition:border-color .16s,background .16s;
  -moz-appearance:textfield}
.blank-input::-webkit-inner-spin-button,.blank-input::-webkit-outer-spin-button{-webkit-appearance:none}
.blank-input:focus{border-bottom-color:var(--teal);background:rgba(31,107,99,.12)}
.blank-input.ti-right{border-bottom-color:var(--teal);background:#e6f4f2;color:var(--teal)}
.blank-input.ti-wrong{border-bottom-color:var(--terra);background:#faeae5;color:var(--terra-deep);animation:shake .3s}
.blank-input:disabled{opacity:1}

@media (max-width:480px){
  .fill-eq{font-size:2rem}
  .blank-input{width:96px;font-size:1.5rem}
}