:root{
  --pink:#E85D8C;--blue:#4A9EF5;--purple:#8B5CF6;--orange:#F59E0B;--teal:#14B8A6;
  --bg:#FFF9F3;--card:#FFFFFF;--text:#3D3D4E;--muted:#A0A0B8;
  --shadow-sm:0 2px 8px rgba(0,0,0,0.06);--shadow-md:0 8px 24px rgba(0,0,0,0.09);
}
html,body{background:var(--bg);font-family:'Nunito',sans-serif;color:var(--text);min-height:100vh;-webkit-tap-highlight-color:transparent}

/* NAV */
nav{background:#fff;box-shadow:0 2px 12px rgba(0,0,0,0.06);padding:0 20px;position:sticky;top:0;z-index:100}
.nav-inner{max-width:960px;margin:0 auto;display:flex;align-items:center;justify-content:space-between;height:56px}
.logo{font-family:'Fredoka',cursive;font-size:22px;font-weight:700;color:var(--pink);text-decoration:none}
.nav-back{font-size:13px;font-weight:800;color:var(--muted);text-decoration:none;display:flex;align-items:center;gap:4px;transition:color 0.2s}
.nav-back:hover{color:var(--purple)}
.nav-links{display:flex;gap:20px;list-style:none}
@media(max-width:760px){.nav-links{display:none}}

/* LAYOUT */
#app{max-width:700px;margin:0 auto;padding:16px 14px 12px}

/* TOP BAR */
.topbar{display:flex;align-items:center;justify-content:space-between;margin-bottom:12px}
.game-title{font-family:'Fredoka',cursive;font-size:22px;font-weight:700;color:var(--text)}
.game-title span{color:var(--blue)}

/* STATS */
.stat-row{display:flex;gap:8px;margin-bottom:14px}
.stat{background:var(--card);border-radius:14px;padding:7px 16px;text-align:center;box-shadow:var(--shadow-sm);border:1.5px solid rgba(0,0,0,0.04);flex:1}
.stat-v{font-family:'Fredoka',cursive;font-size:20px;font-weight:700;color:var(--pink);line-height:1.1}
.stat-v.blue{color:var(--blue)}
.stat-v.purple{color:var(--purple)}
.stat-l{font-size:9px;color:var(--muted);text-transform:uppercase;letter-spacing:1px;font-weight:800}

/* DIFFICULTY */
.diff-wrap{margin-bottom:14px}
.diff-label{font-size:11px;color:var(--muted);font-weight:800;margin-bottom:6px;letter-spacing:0.5px}
.diff-btns{display:flex;gap:8px}
.dbtn{background:var(--card);border:2px solid #EDE5F5;color:var(--purple);font-size:13px;font-weight:800;border-radius:24px;padding:7px 20px;cursor:pointer;transition:all 0.2s;font-family:'Nunito',sans-serif;flex:1;text-align:center}
.dbtn:hover{transform:translateY(-1px);box-shadow:var(--shadow-sm)}
.dbtn.active{background:var(--purple);color:#fff;border-color:var(--purple);box-shadow:0 4px 14px rgba(139,92,246,0.3)}

/* HINT */
.hint{background:var(--card);border-radius:12px;padding:9px 16px;font-size:13px;color:var(--muted);text-align:center;box-shadow:var(--shadow-sm);margin-bottom:14px;font-weight:700;line-height:1.5}
.hint b{color:var(--purple)}

/* START BTN */
.btn-start{width:100%;background:linear-gradient(135deg,var(--blue),var(--teal));color:#fff;border:none;border-radius:14px;padding:12px;font-size:15px;font-weight:900;font-family:'Nunito',sans-serif;cursor:pointer;box-shadow:0 4px 16px rgba(74,158,245,0.3);transition:all 0.15s;margin-bottom:18px;letter-spacing:0.3px}
.btn-start:hover{transform:translateY(-1px);box-shadow:0 6px 20px rgba(74,158,245,0.4)}
.btn-start:active{transform:scale(0.97)}

/* PROGRESS */
.progress-row{display:flex;justify-content:center;gap:5px;margin-bottom:16px;flex-wrap:wrap}
.pdot{width:10px;height:10px;border-radius:50%;background:#E8E0F0;transition:all 0.3s cubic-bezier(.34,1.56,.64,1)}
.pdot.matched{background:var(--teal);transform:scale(1.2);box-shadow:0 0 6px rgba(20,184,166,0.4)}

/* FULLSCREEN BTN */
.btn-icon{background:var(--card);border:2px solid #EDE5F5;color:var(--purple);font-size:18px;border-radius:10px;padding:4px 9px;cursor:pointer;transition:all 0.2s;line-height:1;font-family:sans-serif;display:flex;align-items:center}
.btn-icon:hover{background:var(--purple);color:#fff;border-color:var(--purple)}

/* CARD GRID */
.card-grid{display:grid;gap:10px;justify-content:center}
.card-grid.easy{grid-template-columns:repeat(4,1fr)}
.card-grid.medium{grid-template-columns:repeat(6,1fr)}
.card-grid.hard{grid-template-columns:repeat(8,1fr)}

/* CARD */
.card-wrap{cursor:pointer;perspective:600px;min-width:0}
.card-inner{width:100%;height:100%;position:relative;transform-style:preserve-3d;transition:transform 0.45s cubic-bezier(.4,0,.2,1)}
.card-wrap.flipped .card-inner{transform:rotateY(180deg)}
.card-wrap.matched .card-inner{transform:rotateY(180deg)}

.card-face{position:absolute;inset:0;border-radius:12px;display:flex;align-items:center;justify-content:center;backface-visibility:hidden;-webkit-backface-visibility:hidden;user-select:none}

/* BACK face (shown when face-down) */
.card-back{background:linear-gradient(135deg,var(--purple),var(--blue));box-shadow:var(--shadow-sm)}
.card-back-inner{width:60%;height:60%;border-radius:8px;background:rgba(255,255,255,0.18);display:flex;align-items:center;justify-content:center;font-family:'Fredoka',cursive;font-size:clamp(14px,3vw,20px);color:rgba(255,255,255,0.8);font-weight:700;letter-spacing:-0.5px}

/* FRONT face (shown when flipped) */
.card-front{transform:rotateY(180deg);flex-direction:column;gap:4px;padding:6px;text-align:center}
.card-front.en{background:linear-gradient(135deg,#EFF6FF,#DBEAFE);border:2px solid #BFDBFE}
.card-front.zh{background:linear-gradient(135deg,#FDF4FF,#F3E8FF);border:2px solid #E9D5FF}
.card-wrap.matched .card-front.en{background:linear-gradient(135deg,#F0FFF4,#DCFCE7);border-color:#BBF7D0}
.card-wrap.matched .card-front.zh{background:linear-gradient(135deg,#F0FFF4,#DCFCE7);border-color:#BBF7D0}
.card-wrap.wrong .card-front{animation:wrongShake 0.4s ease}
@keyframes wrongShake{0%,100%{transform:rotateY(180deg) translateX(0)}25%{transform:rotateY(180deg) translateX(-4px)}75%{transform:rotateY(180deg) translateX(4px)}}

.word-en{font-family:'Nunito',sans-serif;font-weight:900;color:var(--blue);line-height:1.1}
.word-zh{font-family:'Nunito',sans-serif;font-weight:800;color:var(--purple);line-height:1.1}
.word-icon{font-size:clamp(14px,3vw,20px)}

/* matched glow */
.card-wrap.matched .card-face.card-front{box-shadow:0 0 0 2px var(--teal),0 4px 12px rgba(20,184,166,0.25)}

/* OVERLAY */
.overlay{position:fixed;inset:0;background:rgba(139,92,246,0.15);backdrop-filter:blur(6px);z-index:200;display:flex;align-items:center;justify-content:center;padding:20px}
.modal{background:#fff;border-radius:24px;padding:36px 28px;text-align:center;max-width:360px;width:100%;box-shadow:0 20px 60px rgba(0,0,0,0.15);animation:modalIn 0.4s cubic-bezier(.34,1.56,.64,1)}
@keyframes modalIn{from{transform:scale(0.8);opacity:0}to{transform:scale(1);opacity:1}}
.modal .em{font-size:64px;margin-bottom:8px}
.modal h2{font-family:'Fredoka',cursive;font-size:28px;font-weight:700;margin-bottom:6px}
.modal .sub{font-size:14px;color:var(--muted);font-weight:700;margin-bottom:20px}
.chips{display:flex;gap:8px;flex-wrap:wrap;justify-content:center;margin-bottom:24px}
.chip{background:#F5F3FF;color:var(--purple);font-size:13px;font-weight:800;border-radius:20px;padding:5px 14px}
.chip.teal{background:#F0FFF4;color:var(--teal)}
.chip.orange{background:#FFF7ED;color:var(--orange)}
.modal .btn-go{width:100%;background:linear-gradient(135deg,var(--blue),var(--teal));color:#fff;border:none;border-radius:14px;padding:12px;font-size:15px;font-weight:900;font-family:'Nunito',sans-serif;cursor:pointer;margin-bottom:10px;box-shadow:0 4px 16px rgba(74,158,245,0.3)}
.modal .btn-go:hover{opacity:0.9}

/* CONFETTI canvas */
canvas#ptx{position:fixed;inset:0;pointer-events:none;z-index:99}

/* sticky footer: pin footer to viewport bottom on short pre-game screens */
body{display:flex;flex-direction:column;min-height:100vh}
#app{flex:1 0 auto}