:root{
  /* ---- light theme = default, matches reference screenshots ---- */
  --bg:#e9ebf3;
  --topbar-bg:#eef0f7;
  --text:#2e3555;
  --text-dim:#8890ab;
  --badge:#c8712f;

  --tape-bg:#eef0f7;
  --tape-line:rgba(46,53,85,0.08);
  --positive:#2e3555;
  --negative:#2e3555;

  --key-num-bg:#f3f4f9;
  --key-op-bg:#b9c4dd;
  --key-op-text:#2e3555;
  --key-ac-bg:#cc6b3d;
  --key-ac-text:#ffffff;
  --key-back-bg:#5c6b8a;
  --key-back-text:#ffffff;
  --key-mem-bg:#eceef5;
  --key-mem-text:#a7aec2;
  --key-mem-active-bg:#b9c4dd;
  --key-mem-active-text:#2e3555;
  --key-custom-bg:#eceef5;
  --key-custom-text:#8890ab;

  --drawer-bg:#ffffff;
  --card-shadow:0 10px 30px rgba(30,35,60,0.18);
  --border:rgba(46,53,85,0.1);
  --radius:18px;
  --safe-bottom: env(safe-area-inset-bottom, 0px);
}

[data-theme="dark"]{
  --bg:#14141f;
  --topbar-bg:#1b1b29;
  --text:#eef0f7;
  --text-dim:#7d84a0;
  --tape-bg:#191926;
  --tape-line:rgba(255,255,255,0.08);
  --positive:#eef0f7;
  --negative:#eef0f7;
  --key-num-bg:#232333;
  --key-op-bg:#3a4568;
  --key-op-text:#eef0f7;
  --key-mem-bg:#232333;
  --key-mem-text:#5b6280;
  --key-mem-active-bg:#3a4568;
  --key-mem-active-text:#eef0f7;
  --key-custom-bg:#232333;
  --key-custom-text:#7d84a0;
  --drawer-bg:#1b1b29;
  --border:rgba(255,255,255,0.1);
}

*{box-sizing:border-box; -webkit-tap-highlight-color:transparent;}
html,body{height:100%;}
body{
  margin:0;
  font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;
  background:var(--bg);
  color:var(--text);
  min-height:100vh;
  overflow:hidden;
  user-select:none;
}
.hidden{display:none !important;}

.app{
  display:flex;
  flex-direction:column;
  height:100vh;
  max-width:480px;
  margin:0 auto;
  padding:6px 12px calc(6px + var(--safe-bottom));
  position:relative;
}

/* ---------- top bar ---------- */
.topbar{
  display:flex;
  align-items:center;
  justify-content:space-between;
  padding:10px 2px 12px;
}
.doc-title{font-size:19px; font-weight:500; color:var(--text);}
.free-badge{
  color:var(--badge); font-weight:700; font-size:14px; letter-spacing:.3px;
  background:none; border:none; cursor:default;
}
.icon-btn{
  width:32px; height:32px; border:none; background:none;
  color:var(--text); font-size:20px; cursor:pointer;
  display:flex; align-items:center; justify-content:center;
}
.icon-btn.small{width:26px; height:26px; font-size:15px; color:var(--text-dim);}

/* ---------- drawers / overlays ---------- */
.drawer-overlay{ position:fixed; inset:0; background:rgba(20,20,30,0.4); z-index:30; }
.drawer{
  position:fixed; top:0; left:0; bottom:0; width:84%; max-width:340px;
  background:var(--drawer-bg); z-index:40;
  transform:translateX(-105%); transition:transform .22s ease;
  display:flex; flex-direction:column; padding:20px 18px;
  box-shadow:var(--card-shadow);
}
.drawer.open{transform:translateX(0);}
.drawer-header{display:flex; justify-content:space-between; align-items:center; font-size:19px; font-weight:700; padding-bottom:16px; color:var(--text);}
.link-btn{background:none;border:none;color:var(--text-dim);font-size:14px;cursor:pointer;}
.link-btn.big{font-size:24px; line-height:1; color:var(--text-dim); font-weight:400;}
.doc-list{flex:1; overflow-y:auto;}
.doc-item{
  padding:12px 8px; border-radius:12px; margin-bottom:4px;
  background:transparent; cursor:pointer;
  display:flex; justify-content:space-between; align-items:center;
}
.doc-item.active{background:rgba(46,53,85,0.06);}
.doc-item .di-name{font-weight:500; font-size:16px; font-style:italic; color:var(--text);}
.doc-item .di-date{font-size:12px; color:var(--text-dim); margin-top:2px; font-style:normal;}
.doc-item .di-del{background:none;border:none;color:var(--text-dim);font-size:14px;padding:4px;}
.drawer-footer{border-top:1px solid var(--border); padding-top:8px; margin-top:8px;}
.drawer-action{
  display:flex; align-items:center; gap:10px; width:100%; text-align:left;
  background:none; border:none; border-bottom:1px solid var(--border);
  color:var(--text); font-size:15px; padding:13px 4px; cursor:pointer;
}
.drawer-action:last-child{border-bottom:none;}

/* ---------- overflow menu ---------- */
.overflow-menu{
  position:absolute; top:46px; right:8px; z-index:41;
  background:var(--drawer-bg); border-radius:16px; overflow:hidden; min-width:230px;
  box-shadow:var(--card-shadow);
}
.overflow-menu button{
  display:flex; align-items:center; gap:14px; width:100%;
  background:none; border:none; color:var(--text); font-size:15px;
  padding:13px 16px; text-align:left; cursor:pointer;
  border-bottom:1px solid var(--border);
}
.overflow-menu button .oi{width:20px; text-align:center; color:var(--text-dim); font-size:16px;}
.overflow-menu button:last-child{border-bottom:none;}
.overflow-menu .menu-divider{height:1px; background:var(--border); margin:0;}

/* ---------- modal ---------- */
.modal{position:fixed; inset:0; background:rgba(0,0,0,0.4); z-index:50; display:flex; align-items:center; justify-content:center;}
.modal-card{ background:var(--drawer-bg); border-radius:18px; width:88%; max-width:360px; padding:16px; box-shadow:var(--card-shadow);}
.modal-header{display:flex; justify-content:space-between; align-items:center; font-size:16px; font-weight:700; padding-bottom:10px;}
.row-toggle{display:flex; justify-content:space-between; align-items:center; padding:10px 2px; border-bottom:1px solid var(--border); font-size:14px;}
.modal-note{font-size:12px; color:var(--text-dim); padding-top:12px; text-align:center;}

.switch{position:relative;width:42px;height:24px; flex:0 0 auto;}
.switch input{opacity:0;width:0;height:0;}
.slider{position:absolute;cursor:pointer;inset:0;background:#c7cbdb;border-radius:24px;transition:.2s;}
.slider:before{content:"";position:absolute;height:18px;width:18px;left:3px;top:3px;background:white;border-radius:50%;transition:.2s;box-shadow:0 1px 3px rgba(0,0,0,0.3);}
input:checked + .slider{background:var(--key-ac-bg);}
input:checked + .slider:before{transform:translateX(18px);}

/* ---------- keyboard/mode bar ---------- */
.kbar{
  display:flex; align-items:center; gap:8px;
  padding:2px 2px 10px;
}
.k-tab{
  padding:5px 12px; border-radius:8px; border:none;
  background:var(--key-mem-bg); color:var(--text-dim); font-size:13px; font-weight:600; cursor:pointer;
}
.k-tab.active{background:var(--key-op-bg); color:var(--key-op-text);}
.kbar-total{
  flex:1; text-align:right; font-size:22px; font-weight:600; color:var(--text); padding-right:6px;
}

/* ---------- Paper Tape (main screen) ---------- */
.tape-wrap{
  flex:1 1 auto;
  min-height:0;
  border-radius:14px;
  background:var(--tape-bg);
  overflow:hidden;
  position:relative;
}
.tape-scroll{height:100%; overflow-y:auto; padding:8px 6px 4px;}
.tape-empty{text-align:center; color:var(--text-dim); font-size:13px; padding:26px 10px;}

.tape-entry{
  display:flex; justify-content:flex-end; align-items:flex-start; gap:10px;
  padding:2px 6px; font-size:20px; font-weight:400; color:var(--text);
}
.tape-entry.subtotal{ border-top:1.5px solid var(--text); margin-top:4px; padding-top:6px; font-weight:600;}
.tape-entry .te-op{width:14px; color:var(--text); flex:0 0 auto; font-weight:400;}
.tape-entry .te-left{flex:1; min-width:0; display:flex; flex-direction:column; align-items:flex-end;}
.tape-entry .te-expr{color:var(--text); font-size:20px; text-align:right;}
.tape-entry .te-note{color:var(--text-dim); font-size:12px; font-style:italic; margin-top:1px;}
.tape-entry .te-result{display:none;} /* expression itself already shows the running value like the reference app */
.tape-entry .te-del{background:none; border:none; color:var(--text-dim); font-size:13px; cursor:pointer; padding:2px; flex:0 0 auto; opacity:.5;}

/* ---------- current entry strip ---------- */
.entry-strip{padding:4px 4px 2px; text-align:right;}
.label-input-wrap{padding-bottom:4px;}
.label-input-wrap input{
  width:100%; text-align:right; background:var(--key-mem-bg); border:none;
  color:var(--text); border-radius:10px; padding:8px 10px; font-size:13px;
}
.expression{font-size:14px; color:var(--text-dim); min-height:16px; word-break:break-all;}
.result{font-size:30px; font-weight:600; word-break:break-all; color:var(--text);}
.result.pulse{opacity:.7;}

.mode-toggle{display:flex; gap:8px; padding:6px 2px 4px;}
.mode-btn{
  flex:1; padding:6px 0; border-radius:10px; border:none;
  background:var(--key-mem-bg); color:var(--text-dim); font-size:11px; font-weight:600; cursor:pointer;
}
.mode-btn.active{background:var(--key-op-bg); color:var(--key-op-text);}

.pad{display:grid; grid-template-columns:repeat(4,1fr); gap:8px; padding:4px 0;}
.sci-row{padding-bottom:6px;}

.key{
  position:relative; overflow:hidden; border:none;
  background:var(--key-num-bg); color:var(--text); border-radius:14px;
  font-size:22px; font-weight:400; padding:14px 0; cursor:pointer;
  transition:transform .08s ease, filter .15s ease;
}
.key:active{filter:brightness(0.94);}
.key.op{background:var(--key-op-bg); color:var(--key-op-text); font-weight:500;}
.key.op-light{background:var(--key-op-bg); color:var(--key-op-text); font-size:16px; font-weight:500;}
.key.fn{font-size:13px; padding:11px 0; background:var(--key-mem-bg); color:var(--text-dim);}
.key.mem{background:var(--key-mem-bg); color:var(--key-mem-text); font-size:15px; font-weight:500;}
.key.mem.active{background:var(--key-mem-active-bg); color:var(--key-mem-active-text);}
.key.custom{background:var(--key-custom-bg); color:var(--key-custom-text); font-size:12px; font-weight:500; line-height:1.35;}
.key.equals{background:var(--key-op-bg); color:var(--key-op-text); font-weight:500; font-size:15px;}
.key[data-action="clear"]{background:var(--key-ac-bg); color:var(--key-ac-text); font-weight:600;}
.key[data-action="backspace"]{background:var(--key-back-bg); color:var(--key-back-text);}

.ripple{position:absolute; border-radius:50%; background:rgba(0,0,0,0.15); transform:scale(0); animation:ripple .5s ease-out; pointer-events:none;}
[data-theme="dark"] .ripple{background:rgba(255,255,255,0.2);}
@keyframes ripple{ to{transform:scale(3); opacity:0;} }

.ad-slot{min-height:36px; margin-top:2px; border-radius:14px;}

/* ---------- floating cast/scroll button (bottom-right of tape) ---------- */
.fab{
  position:absolute; right:16px; bottom:16px; z-index:5;
  width:48px; height:48px; border-radius:14px;
  background:#ffffff; border:none; box-shadow:var(--card-shadow);
  color:var(--text); font-size:18px; cursor:pointer;
  display:flex; align-items:center; justify-content:center;
}

.toast{
  position:fixed; left:50%; bottom:90px; transform:translateX(-50%);
  background:var(--text); color:var(--bg); padding:10px 18px; border-radius:12px;
  font-size:13px; z-index:60; opacity:0; transition:opacity .2s ease; pointer-events:none;
}
.toast.show{opacity:1;}

@media print{
  .topbar,.kbar,.mode-toggle,.pad,.ad-slot,.entry-strip,.drawer,.overflow-menu,.modal,.fab{display:none !important;}
  body{background:#fff; color:#000; overflow:visible;}
  .tape-wrap{background:#fff; height:auto; overflow:visible;}
  .tape-scroll{height:auto; overflow:visible;}
  .tape-entry{color:#000 !important;}
}