* { box-sizing: border-box; margin: 0; }
/* an author-level display rule outranks the browser's own
   [hidden] { display: none }, so say it here or hiding a flex
   container does nothing at all */
[hidden] { display: none !important; }

:root {
  --bg: #f4f2ec; --card: #fff; --line: #d9d5cc; --text: #222;
  --muted: #666; --blue: #2266cc; --blue-soft: #eef3ff;
  --green: #1f9a6a; --red: #8a1c12;
}
html { color-scheme: light; }
body {
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  padding: 8px 8px 24px;
  max-width: 760px;
  margin: 0 auto;
  line-height: 1.35;
}
button { font: inherit; color: inherit; cursor: pointer; }
button:disabled { cursor: default; }
:focus-visible { outline: 3px solid #ffb400; outline-offset: 2px; }

/* ---------------- header / tabs ---------------- */
header { display: flex; align-items: center; justify-content: space-between;
         gap: 8px; margin: 2px 0 8px; }
h1 { font-size: 1.15rem; line-height: 1.2; }
#tagline { display: none; color: var(--muted); font-size: 0.85rem;
           margin-top: 2px; }
@media (min-width: 600px) {
  h1 { font-size: 1.5rem; }
  #tagline { display: block; }
}
.mini { min-width: 36px; min-height: 36px; padding: 0 10px;
        font-size: 0.95rem; border: 1px solid #bbb; border-radius: 8px;
        background: #fff; }
.mini:disabled { opacity: 0.45; }

#modes { display: flex; gap: 6px; margin: 0 0 8px; }
.tab { flex: 1; padding: 9px; font-size: 0.95rem; font-weight: 600;
       border: 2px solid #bbb; border-radius: 8px; background: #fff;
       color: #555; }
.tab[aria-selected="true"] { border-color: var(--blue);
                             background: var(--blue-soft); color: var(--blue); }

/* ---------------- layout ---------------- */
#layout { display: flex; flex-direction: column; gap: 10px; }
#board-col, #side-col, #editor-panel { min-width: 0; display: flex;
                                       flex-direction: column; gap: 10px; }

#board-wrap { position: relative; width: 100%; overflow-x: auto;
              touch-action: none; }
#board { display: block; margin: 0 auto; touch-action: none;
         user-select: none; -webkit-user-select: none;
         -webkit-touch-callout: none; }
#board-hint { position: absolute; left: 50%; top: 14px;
              transform: translateX(-50%); background: rgba(20,20,20,0.82);
              color: #fff; padding: 8px 14px; border-radius: 999px;
              font-size: 0.85rem; pointer-events: none; white-space: nowrap;
              max-width: calc(100% - 24px); overflow: hidden;
              text-overflow: ellipsis; }

.msg { white-space: pre-wrap; font-size: 0.85rem; padding: 8px 10px;
       border-radius: 8px; border-left: 4px solid transparent; }
.msg.info { background: #e7f3ec; color: #1f5b36; border-color: #3a9a65; }
.msg.warn { background: #fff3dc; color: #6f4400; border-color: #e0a030; }
.msg.error { background: #fbe7e5; color: #8a1c12; border-color: #d0463a; }

/* ---------------- results ---------------- */
#results { display: flex; flex-direction: column; gap: 8px; }
.stats { display: flex; flex-wrap: wrap; align-items: center; gap: 6px 16px;
         background: #fff; border: 1px solid var(--line); border-radius: 10px;
         padding: 10px 12px; }
.stat { display: flex; flex-direction: column; }
.stat-v { font-size: 1.25rem; font-weight: 700; line-height: 1.1; }
.stat-l { font-size: 0.72rem; color: var(--muted); }
.badge { margin-left: auto; font-size: 0.75rem; font-weight: 600;
         padding: 3px 9px; border-radius: 999px; background: #e7f3ec;
         color: #1f5b36; white-space: nowrap; }
.badge.warn { background: #fff3dc; color: #6f4400; }
.badge.plain { background: #eee; color: #444; }
.plan-lines { list-style: none; padding: 0 2px; margin: 0; font-size: 0.85rem;
              display: flex; flex-direction: column; gap: 3px; }
.coord { font: inherit; font-weight: 600; color: var(--blue); background: none;
         border: 0; padding: 4px 5px; margin: -4px 0; border-radius: 4px;
         text-decoration: underline dotted; }
#pan-hint { font-size: 0.78rem; color: var(--muted); text-align: center;
            margin-top: -4px; }
.coord:hover { background: var(--blue-soft); }

#chips-wrap { position: relative; }
#chips { display: flex; overflow-x: auto; gap: 6px; padding: 2px 0 6px;
         scroll-snap-type: x proximity; -webkit-overflow-scrolling: touch; }
#chips-wrap.can-scroll:not(.at-end)::after {
  content: ""; position: absolute; top: 0; right: 0; bottom: 6px; width: 44px;
  background: linear-gradient(to right, rgba(244,242,236,0), var(--bg));
  pointer-events: none; }
.chip { flex: 0 0 auto; scroll-snap-align: start; display: flex;
        flex-direction: column; align-items: center; border: 2px solid #bbb;
        border-radius: 12px; background: #fff; padding: 6px 12px;
        min-width: 92px; }
.chip-inc { font-weight: 700; font-size: 1rem; line-height: 1.15; }
.chip-inc small { font-weight: 500; font-size: 0.72rem; color: var(--muted); }
.chip-cost { font-size: 0.75rem; color: var(--muted); }
.chip[aria-pressed="true"] { border-color: var(--blue);
                             background: var(--blue-soft); }

/* ---------------- editor palette ---------------- */
#editor-bar { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; }
.ctl { display: flex; align-items: center; gap: 4px; }
.ctl-label { font-size: 0.8rem; color: var(--muted); margin-right: 2px; }
#width-label { min-width: 1.8em; text-align: center; font-weight: 600; }
.ctl { margin-right: 6px; }

#tools { display: flex; flex-direction: column; gap: 8px; }
.tool-group { display: flex; flex-direction: column; gap: 3px; }
.tool-cap { font-size: 0.72rem; font-weight: 600; text-transform: uppercase;
            letter-spacing: 0.04em; color: var(--muted); }
.tool-cap .legend { text-transform: none; letter-spacing: 0;
                    font-weight: 400; margin-left: 6px; }
.tool-row { display: flex; flex-wrap: wrap; gap: 6px; }
.tool { display: flex; flex-direction: column; align-items: center; gap: 3px;
        border: 2px solid #ccc; border-radius: 8px; background: #fff;
        padding: 5px 6px 4px; min-width: 50px; font-size: 0.72rem;
        color: #444; flex: 0 0 auto; }
.tool[aria-pressed="true"] { border-color: var(--blue);
                             background: var(--blue-soft); color: var(--blue); }

#options { display: flex; flex-wrap: wrap; gap: 4px 14px; font-size: 0.85rem; }
#options label { display: flex; align-items: center; gap: 5px;
                 min-height: 28px; }

/* ---------------- buttons ---------------- */
.btn { width: 100%; min-height: 46px; padding: 10px 12px; font-size: 1.05rem;
       font-weight: 700; border-radius: 10px; border: 2px solid transparent; }
.btn.primary { background: var(--blue); color: #fff; border-color: var(--blue); }
.btn.primary.go { background: var(--green); border-color: var(--green); }
.btn.secondary { background: #fff; color: var(--blue); border-color: var(--blue); }
.btn.tertiary { background: #fff; color: #444; border-color: #bbb; }
.btn:disabled { opacity: 0.55; }
.btn-row { display: flex; flex-direction: column; gap: 8px; }

#progress { display: flex; align-items: center; gap: 10px; margin-top: 8px; }
#progress .bar { flex: 1; height: 8px; background: #e2ded4;
                 border-radius: 4px; overflow: hidden; }
#progress .fill { height: 100%; width: 0; background: var(--blue);
                  border-radius: 4px; transition: width 0.3s; }
#progress.indeterminate .fill { width: 35%; transition: none;
                                animation: slide 1.2s ease-in-out infinite; }
@keyframes slide { from { margin-left: -35%; } to { margin-left: 100%; } }
#progress-text { font-size: 0.8rem; color: var(--muted); min-width: 3.5em;
                 text-align: right; }

/* ---------------- challenge ---------------- */
#challenge-bar { display: flex; flex-direction: column; gap: 10px; }
#ch-card { background: #fff; border: 1px solid var(--line); border-radius: 10px;
           padding: 10px 12px; display: flex; flex-direction: column; gap: 8px; }
#ch-goal { font-size: 0.9rem; }
#ch-live { display: flex; flex-wrap: wrap; gap: 6px 18px; align-items: center; }
#ch-result { border-top: 1px solid var(--line); padding-top: 8px;
             font-size: 0.9rem; }
#ch-result .stars { font-size: 1.7rem; color: #d90; letter-spacing: 2px;
                    line-height: 1.1; }
#ch-result .problems { color: var(--red); font-size: 0.8rem; margin-top: 6px; }

/* ---------------- footer ---------------- */
footer { margin-top: 28px; padding-top: 12px; border-top: 1px solid var(--line);
         font-size: 0.78rem; color: var(--muted); display: flex;
         flex-direction: column; gap: 4px; }
footer a, .kofi-line a { color: var(--blue); }

/* the post-solve donation line: same muted hint style as #pan-hint */
.kofi-line { margin: 10px 0 0; font-size: 0.78rem; color: var(--muted); }

/* ---------------- help ---------------- */
#help-overlay { position: fixed; inset: 0; background: rgba(0,0,0,0.45);
                z-index: 20; display: flex; align-items: flex-start;
                justify-content: center; padding: 12px; }
#help-panel { background: #fff; border-radius: 12px; max-width: 560px;
              width: 100%; max-height: calc(100vh - 24px);
              overflow-y: auto; padding: 14px; font-size: 0.85rem;
              line-height: 1.45; }
#help-head { display: flex; align-items: center;
             justify-content: space-between; margin-bottom: 6px; }
#help-head h2 { font-size: 1rem; }
#help-panel p { margin: 6px 0; }
#help-panel details { border-top: 1px solid #eee; padding: 7px 0; }
#help-panel summary { font-weight: bold; cursor: pointer; padding: 3px 0; }
#help-panel ul, #help-panel ol { padding-left: 1.2em; margin: 6px 0; }
#help-panel li { margin: 4px 0; }
body.modal-open { overflow: hidden; }

/* ---------------- desktop: board left, controls right ---------------- */
@media (min-width: 900px) {
  body { max-width: 1120px; padding: 12px 16px 28px; }
  #layout { display: grid; grid-template-columns: minmax(0, 1fr) 380px;
            gap: 20px; align-items: start; }
}