/* Pocket Teacher - black & white dark theme.
   Every color comes from this palette: change it here to restyle the whole app. */
:root {
  color-scheme: dark;
  --bg: #0a0a0a;          /* page background */
  --panel: #111111;       /* cards, top bar, composer */
  --panel-2: #181818;     /* inputs, hover */
  --sidebar: #000000;
  --border: #262626;
  --border-strong: #3a3a3a;
  --text: #f5f5f5;
  --muted: #8f8f8f;
  --accent: #ffffff;      /* primary buttons, student bubbles */
  --accent-text: #000000; /* text on accent */
  --radius: 14px;
}

* { box-sizing: border-box; }
html, body { margin: 0; height: 100%; }
body {
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}
button, input, textarea { font: inherit; color: inherit; }
.hidden { display: none !important; }
::selection { background: var(--accent); color: var(--accent-text); }

/* ---------- buttons ---------- */
button { cursor: pointer; border: 0; border-radius: 10px; padding: 10px 16px; background: transparent; transition: background .15s, border-color .15s, opacity .15s; }
.primary { background: var(--accent); color: var(--accent-text); font-weight: 600; }
.primary:hover { background: #d9d9d9; }
.primary:disabled { opacity: .5; cursor: default; }
.ghost { color: var(--text); border: 1px solid var(--border-strong); }
.ghost:hover { border-color: var(--text); }
.full { width: 100%; }
.icon-btn { font-size: 22px; padding: 4px 10px; display: none; color: var(--text); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ---------- logo ---------- */
.brand { font-size: 22px; font-weight: 800; letter-spacing: -0.02em; display: flex; align-items: center; gap: 10px; }
.brand.small { font-size: 17px; }
.logo {
  display: inline-grid; place-items: center; width: 30px; height: 30px; border-radius: 8px;
  background: var(--accent); color: var(--accent-text); font-size: 16px; font-weight: 900;
}
.brand.small .logo { width: 26px; height: 26px; font-size: 14px; }

/* ---------- auth ---------- */
.auth { min-height: 100%; display: grid; place-items: center; padding: 16px; }
.auth-card {
  width: 100%; max-width: 400px; background: var(--panel); border: 1px solid var(--border);
  border-radius: 20px; padding: 32px 24px;
}
.tagline { color: var(--muted); margin: 8px 0 24px; }
.tabs { display: flex; background: var(--bg); border: 1px solid var(--border); border-radius: 12px; padding: 4px; margin-bottom: 20px; }
.tab { flex: 1; color: var(--muted); font-weight: 600; }
.tab.active { background: var(--accent); color: var(--accent-text); }
.form { display: flex; flex-direction: column; gap: 14px; }
.form label { display: flex; flex-direction: column; gap: 6px; font-size: 14px; font-weight: 600; }
.form input {
  padding: 12px; background: var(--panel-2); border: 1px solid var(--border); border-radius: 10px; font-weight: 400;
}
.form input::placeholder, .composer textarea::placeholder { color: #5c5c5c; }
.form input:focus, .composer textarea:focus { outline: none; border-color: var(--text); }
.form .primary { margin-top: 6px; padding: 12px; }
.error { color: var(--text); min-height: 20px; margin: 14px 0 0; font-size: 14px; }
.error:not(:empty)::before { content: "! "; font-weight: 800; }

/* ---------- app layout ---------- */
.app { display: flex; height: 100%; }
.sidebar {
  width: 280px; flex-shrink: 0; background: var(--sidebar); border-right: 1px solid var(--border);
  display: flex; flex-direction: column;
}
.sidebar-top { padding: 18px 14px; display: flex; flex-direction: column; gap: 16px; }
.chat-list { flex: 1; overflow-y: auto; padding: 0 8px; }
.chat-item {
  display: flex; align-items: center; gap: 6px; padding: 10px; border-radius: 8px;
  cursor: pointer; font-size: 14px; color: var(--muted);
}
.chat-item:hover { background: var(--panel-2); color: var(--text); }
.chat-item.active { background: var(--panel-2); color: var(--text); box-shadow: inset 2px 0 0 var(--accent); }
.chat-item .title { flex: 1; overflow: hidden; white-space: nowrap; text-overflow: ellipsis; }
.chat-item .del { color: var(--muted); padding: 2px 6px; visibility: hidden; }
.chat-item:hover .del { visibility: visible; }
.chat-item .del:hover { color: var(--text); }
.empty-history { font-size: 13px; color: var(--muted); padding: 10px; }
.sidebar-bottom {
  border-top: 1px solid var(--border); padding: 14px; display: flex; align-items: center; gap: 10px;
}
.user-name { flex: 1; font-size: 14px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

.main { flex: 1; display: flex; flex-direction: column; min-width: 0; }
.topbar {
  display: flex; align-items: center; gap: 8px; padding: 14px 20px;
  border-bottom: 1px solid var(--border); background: var(--bg);
}
.topbar h1 { font-size: 16px; font-weight: 600; margin: 0; overflow: hidden; white-space: nowrap; text-overflow: ellipsis; }

/* ---------- messages ---------- */
.messages { flex: 1; overflow-y: auto; padding: 24px 20px; display: flex; flex-direction: column; gap: 16px; }
.msg { max-width: 760px; width: fit-content; padding: 12px 16px; border-radius: var(--radius); line-height: 1.6; overflow-wrap: anywhere; }
.msg.user { align-self: flex-end; background: var(--accent); color: var(--accent-text); border-bottom-right-radius: 4px; white-space: pre-wrap; }
.msg.assistant { align-self: flex-start; background: var(--panel); border: 1px solid var(--border); border-bottom-left-radius: 4px; }
.msg.assistant p { margin: 0 0 10px; }
.msg.assistant p:last-child { margin-bottom: 0; }
.msg.assistant h3 { font-size: 16px; margin: 12px 0 6px; }
.msg.assistant ul, .msg.assistant ol { margin: 6px 0 10px; padding-left: 22px; }
.msg.assistant strong { color: #fff; }
.msg.assistant code { background: var(--panel-2); border: 1px solid var(--border); padding: 1px 5px; border-radius: 5px; font-size: 14px; }
.msg.assistant pre { background: #000; border: 1px solid var(--border); padding: 12px; border-radius: 10px; overflow-x: auto; }
.msg.assistant pre code { background: transparent; border: 0; padding: 0; }
.msg.thinking { color: var(--muted); font-style: italic; }
.msg.error-msg { background: transparent; border: 1px dashed var(--text); color: var(--text); }

.welcome { margin: auto; text-align: center; color: var(--muted); max-width: 440px; }
.welcome .big { font-size: 40px; color: var(--text); }
.welcome h2 { color: var(--text); margin: 8px 0; letter-spacing: -0.02em; }
.suggestions { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; margin-top: 18px; }
.suggestions button { border: 1px solid var(--border-strong); color: var(--text); font-size: 14px; border-radius: 999px; }
.suggestions button:hover { border-color: var(--text); }

/* ---------- composer ---------- */
.composer {
  display: flex; gap: 10px; padding: 14px 20px 18px; background: var(--bg); border-top: 1px solid var(--border);
}
.composer textarea {
  flex: 1; resize: none; background: var(--panel); border: 1px solid var(--border); border-radius: 12px;
  padding: 12px; max-height: 180px; line-height: 1.4;
}

/* ---------- question credits & plans ---------- */
.sidebar-credits { padding: 12px 14px; border-top: 1px solid var(--border); font-size: 14px; color: var(--muted); display: flex; flex-direction: column; gap: 10px; }
.sidebar-credits span { font-weight: 700; color: var(--text); }
.upgrade-btn { background: var(--accent); color: var(--accent-text); font-weight: 700; }
.upgrade-btn:hover { background: #d9d9d9; }
.credits-chip {
  margin-left: auto; flex-shrink: 0; border: 1px solid var(--border-strong); color: var(--text);
  font-weight: 600; font-size: 13px; padding: 6px 12px; border-radius: 999px;
}
.credits-chip:hover { border-color: var(--text); }
.credits-chip.low { border-color: var(--text); }
.credits-chip.empty { background: var(--accent); color: var(--accent-text); border-color: var(--accent); }

.modal { position: fixed; inset: 0; background: rgba(0, 0, 0, .75); display: grid; place-items: center; padding: 16px; z-index: 50; }
.modal-card { position: relative; width: 100%; max-width: 560px; background: var(--panel); border: 1px solid var(--border); border-radius: 20px; padding: 28px 24px 20px; max-height: 100%; overflow-y: auto; }
.modal-card h2 { margin: 0 0 6px; letter-spacing: -0.02em; }
.modal-close { position: absolute; top: 12px; right: 12px; color: var(--muted); font-size: 18px; padding: 6px 10px; }
.modal-close:hover { color: var(--text); }
.muted { color: var(--muted); margin: 0 0 18px; }
.muted.small { font-size: 12px; margin: 8px 0 0; text-align: center; }
.plans { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 12px; }
.plan { border: 1px solid var(--border); background: var(--bg); border-radius: 14px; padding: 16px; display: flex; flex-direction: column; gap: 6px; position: relative; }
.plan.best { border: 2px solid var(--accent); }
.plan .badge { position: absolute; top: -11px; left: 14px; background: var(--accent); color: var(--accent-text); font-size: 11px; font-weight: 700; padding: 3px 8px; border-radius: 999px; }
.plan .name { font-weight: 700; }
.plan .price { font-size: 26px; font-weight: 800; letter-spacing: -0.02em; }
.plan .qs { color: var(--muted); font-size: 14px; }
.plan .per { color: var(--muted); font-size: 12px; margin-bottom: 8px; }
.plan button { margin-top: auto; }
.plan.free button { background: var(--panel-2); color: var(--muted); cursor: default; }

.toast { position: fixed; bottom: 24px; left: 50%; transform: translateX(-50%); background: var(--accent); color: var(--accent-text); padding: 12px 18px; border-radius: 12px; z-index: 60; font-weight: 600; box-shadow: 0 8px 30px rgba(0,0,0,.6); max-width: calc(100% - 32px); }

/* ---------- scrollbars ---------- */
* { scrollbar-width: thin; scrollbar-color: var(--border-strong) transparent; }

/* ---------- mobile ---------- */
.backdrop { display: none; }
@media (max-width: 760px) {
  .icon-btn { display: block; }
  .sidebar {
    position: fixed; inset: 0 auto 0 0; z-index: 20; transform: translateX(-100%);
    transition: transform .2s ease;
  }
  .app.menu-open .sidebar { transform: none; }
  .app.menu-open .backdrop { display: block; position: fixed; inset: 0; background: rgba(0,0,0,.7); z-index: 10; }
  .chat-item .del { visibility: visible; }
  .messages { padding: 16px; }
  .composer { padding: 12px 16px 16px; }
  .topbar { padding: 12px 16px; }
}