/* ========================================
   IMPORT & VARIABILI
   ======================================== */

@import url('https://fonts.googleapis.com/css2?family=Playfair+Display:wght@400;700;900&family=Inter:wght@300;400;500;600&display=swap');

:root {
    --bg-color: #070707;
    --text-color: #FCF7F8;
    --accent-color: #961114;
    --accent-dim: rgba(255,59,48,0.15);
    --secondary-bg: #111111;
    --card-bg: #1a1a1a;
    --btn-bg: #1e1e1e;
    --btn-hover: #2a2a2a;
    --btn-active: #333;
    --border-color: rgba(252,247,248,0.07);
    --border-hover: rgba(252,247,248,0.18);
    --nav-height: 70px;
    --font-display: 'Playfair Display', Georgia, serif;
    --font-body: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --transition-theme: background-color 0.5s cubic-bezier(0.4,0,0.2,1),
                        color 0.5s cubic-bezier(0.4,0,0.2,1);
}

body.light-theme {
    --bg-color: #FCF7F8;
    --text-color: #070707;
    --secondary-bg: #eaeaea;
    --card-bg: #e0e0e0;
    --btn-bg: #dcdcdc;
    --btn-hover: #d0d0d0;
    --btn-active: #c4c4c4;
    --border-color: rgba(7,7,7,0.08);
    --border-hover: rgba(7,7,7,0.2);
    --accent-dim: rgba(255,59,48,0.1);
}

* { margin:0; padding:0; box-sizing:border-box; }
html { scroll-behavior: smooth; }

body {
    font-family: var(--font-body);
    background-color: var(--bg-color);
    color: var(--text-color);
    transition: var(--transition-theme);
    min-height: 100vh;
    overflow-x: hidden;
}

/* ========================================
   NAVBAR
   ======================================== */

.navbar {
    position: fixed; top:0; left:0; right:0; z-index:1000;
    background-color: rgba(7,7,7,0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition-theme);
}
body.light-theme .navbar { background-color: rgba(252,247,248,0.85); }

.navbar-container {
    height: var(--nav-height); padding: 0 2rem;
    display: flex; justify-content: space-between; align-items: center;
    max-width: 1800px; margin: 0 auto;
}
.navbar-logo { display:flex; align-items:center; gap:0.75rem; }
.logo-icon { width: auto; height: 40px; flex-shrink: 0; }
.logo-text { font-family:var(--font-display); font-size:1.4rem; font-weight:700; letter-spacing:-0.02em; }
.navbar-links { display:flex; align-items:center; gap:1.5rem; }
.nav-link { color:var(--text-color); text-decoration:none; font-size:0.9rem; font-weight:500; transition:color 0.2s; }
.nav-link:hover { color:var(--accent-color); }

.theme-toggle {
    background:none; border:1px solid var(--border-color); border-radius:50%;
    width:38px; height:38px; display:flex; align-items:center; justify-content:center;
    cursor:pointer; color:var(--text-color); transition:all 0.2s; position:relative;
}
.theme-toggle:hover { border-color:var(--accent-color); transform:rotate(180deg); }
.sun-icon,.moon-icon { position:absolute; transition:opacity 0.2s, transform 0.2s; }
.sun-icon { opacity:0; transform:rotate(-90deg); }
.moon-icon { opacity:1; transform:rotate(0); }
body.light-theme .sun-icon { opacity:1; transform:rotate(0); }
body.light-theme .moon-icon { opacity:0; transform:rotate(90deg); }

/* ========================================
   APP LAYOUT
   ======================================== */

.app-layout {
    display: grid;
    grid-template-columns: 420px 1fr;
    gap: 1.5rem;
    padding: calc(var(--nav-height) + 1.5rem) 1.5rem 2rem;
    min-height: 100vh;
    align-items: start;
}

/* ========================================
   PANNELLO CALCOLATRICE
   ======================================== */

.calc-panel {
    background: var(--secondary-bg);
    border: 1px solid var(--border-color);
    border-radius: 18px;
    overflow: hidden;
    position: sticky;
    top: calc(var(--nav-height) + 1.5rem);
}

/* --- DISPLAY --- */

.display-area {
    padding: 1.2rem 1.4rem 1rem;
    background: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
}

.display-mode-row {
    display: flex;
    align-items: center;
    gap: 0.35rem;
    margin-bottom: 0.7rem;
}

.mode-btn {
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    color: var(--text-color);
    font-size: 0.6rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    padding: 0.28rem 0.55rem;
    cursor: pointer;
    transition: all 0.15s;
    opacity: 0.5;
}
.mode-btn:hover { opacity: 0.8; border-color: var(--border-hover); }
.mode-btn.active {
    background: var(--accent-color);
    border-color: var(--accent-color);
    color: #fff;
    opacity: 1;
}

.graph-toggle-btn {
    margin-left: auto;
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    color: var(--text-color);
    font-size: 0.6rem;
    font-weight: 600;
    letter-spacing: 0.04em;
    padding: 0.28rem 0.6rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.3rem;
    transition: all 0.15s;
    opacity: 0.55;
}
.graph-toggle-btn:hover { opacity: 0.85; border-color: var(--border-hover); }
.graph-toggle-btn.active {
    border-color: var(--accent-color);
    color: var(--accent-color);
    opacity: 1;
}

.display-expression {
    font-size: 0.78rem;
    color: var(--text-color);
    opacity: 0.4;
    min-height: 1.2em;
    text-align: right;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    letter-spacing: 0.01em;
    padding-right: 2px;
}

.display-result {
    font-family: var(--font-display);
    font-size: 2.6rem;
    font-weight: 700;
    text-align: right;
    letter-spacing: -0.02em;
    line-height: 1.15;
    word-break: break-all;
    padding: 0.15rem 0;
    color: var(--text-color);
    transition: color 0.2s;
}
.display-result.error { color: var(--accent-color); }

.display-history {
    margin-top: 0.6rem;
    max-height: 56px;
    overflow-y: auto;
    display: flex;
    flex-direction: column-reverse;
    gap: 0.2rem;
}
.display-history::-webkit-scrollbar { width: 3px; }
.display-history::-webkit-scrollbar-track { background: transparent; }
.display-history::-webkit-scrollbar-thumb { background: var(--border-color); border-radius: 2px; }

.history-item {
    font-size: 0.62rem;
    opacity: 0.3;
    text-align: right;
    cursor: pointer;
    padding: 0.1rem 0;
    transition: opacity 0.15s;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}
.history-item:hover { opacity: 0.7; }

/* --- GRIGLIA SCIENTIFICA --- */

.scientific-grid {
    display: grid;
    grid-template-columns: repeat(6, 1fr);
    gap: 3px;
    padding: 0.7rem 0.7rem 0.4rem;
}

/* --- GRIGLIA PRINCIPALE --- */

.main-grid {
    display: grid;
    grid-template-columns: repeat(6, 1fr);
    gap: 4px;
    padding: 0.4rem 0.7rem 0.7rem;
}

/* --- BOTTONI --- */

.btn {
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-family: var(--font-body);
    font-size: 0.82rem;
    font-weight: 500;
    color: var(--text-color);
    background: var(--btn-bg);
    padding: 0.7rem 0.2rem;
    transition: background 0.12s, transform 0.08s, box-shadow 0.12s;
    display: flex;
    align-items: center;
    justify-content: center;
    user-select: none;
    -webkit-user-select: none;
    outline: none;
}
.btn:hover { background: var(--btn-hover); }
.btn:active { background: var(--btn-active); transform: scale(0.94); }

.btn-fn {
    font-size: 0.68rem;
    padding: 0.5rem 0.15rem;
    border-radius: 6px;
    opacity: 0.75;
}
.btn-fn:hover { opacity: 1; }

.btn-const {
    font-size: 0.72rem;
    font-weight: 600;
    color: var(--accent-color);
    opacity: 0.85;
}
.btn-const:hover { opacity: 1; background: var(--accent-dim); }

.btn-num { font-size: 1.1rem; font-weight: 600; padding: 0.85rem 0.2rem; }

.btn-op { font-size: 0.82rem; font-weight: 500; }
.btn-op.btn-accent {
    background: var(--accent-dim);
    color: var(--accent-color);
    font-size: 1.1rem;
    font-weight: 600;
}
.btn-op.btn-accent:hover { background: rgba(255,59,48,0.25); }

.btn-paren { font-size: 1rem; font-weight: 600; opacity: 0.7; }
.btn-paren:hover { opacity: 1; }

.btn-mem { font-size: 0.62rem; font-weight: 700; letter-spacing: 0.04em; opacity: 0.5; }
.btn-mem:hover { opacity: 0.85; }
.btn-mem.active { opacity: 1; color: var(--accent-color); }

.btn-clear { font-size: 0.75rem; font-weight: 600; opacity: 0.6; }
.btn-clear:hover { opacity: 1; }
#btnAC { color: var(--accent-color); opacity: 0.7; }

.btn-eq {
    background: var(--accent-color);
    color: #fff;
    font-size: 1.2rem;
    font-weight: 700;
    padding: 0.85rem 0.2rem;
    box-shadow: 0 3px 12px rgba(255,59,48,0.3);
}
.btn-eq:hover { background: #e0342a; box-shadow: 0 4px 16px rgba(255,59,48,0.4); }
.btn-eq:active { transform: scale(0.96); }

.span-2 { grid-column: span 2; }

/* ========================================
   PANNELLO GRAFICO
   ======================================== */

.graph-panel {
    background: var(--secondary-bg);
    border: 1px solid var(--border-color);
    border-radius: 18px;
    overflow: hidden;
    display: none;
    flex-direction: column;
    height: calc(100vh - var(--nav-height) - 3rem);
    max-height: 700px;
}
.graph-panel.visible { display: flex; }

.graph-header {
    padding: 0.8rem 1rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 0.7rem;
    flex-wrap: wrap;
}

.graph-input-wrap {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    flex: 1;
    min-width: 180px;
}

.graph-label {
    font-family: var(--font-display);
    font-size: 0.95rem;
    font-weight: 700;
    opacity: 0.6;
    white-space: nowrap;
}

.graph-input {
    flex: 1;
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 7px;
    color: var(--text-color);
    font-family: var(--font-body);
    font-size: 0.8rem;
    font-weight: 500;
    padding: 0.45rem 0.7rem;
    outline: none;
    transition: border-color 0.2s;
}
.graph-input:focus { border-color: var(--accent-color); }
.graph-input::placeholder { opacity: 0.3; }

.graph-controls { display: flex; gap: 0.3rem; }

.graph-btn {
    background: var(--btn-bg);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    color: var(--text-color);
    width: 30px; height: 30px;
    display: flex; align-items: center; justify-content: center;
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: 600;
    transition: all 0.15s;
}
.graph-btn:hover { border-color: var(--accent-color); color: var(--accent-color); background: var(--accent-dim); }

.graph-canvas-wrap {
    flex: 1;
    position: relative;
    overflow: hidden;
    background: var(--card-bg);
}

#graphCanvas {
    width: 100%;
    height: 100%;
    display: block;
    cursor: grab;
}
#graphCanvas:active { cursor: grabbing; }

.graph-error {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: var(--accent-color);
    font-size: 0.78rem;
    font-weight: 500;
    text-align: center;
    padding: 0 1rem;
    opacity: 0;
    transition: opacity 0.25s;
    pointer-events: none;
}
.graph-error.visible { opacity: 1; }

/* ========================================
   RESPONSIVE
   ======================================== */

@media (max-width: 900px) {
    .app-layout {
        grid-template-columns: 1fr;
        max-width: 460px;
        margin: 0 auto;
    }
    .calc-panel { position: static; }
    .graph-panel { max-height: 420px; }
}

@media (max-width: 480px) {
    .app-layout { padding-left: 0.6rem; padding-right: 0.6rem; }
    .calc-panel { border-radius: 14px; }
    .scientific-grid { gap: 2px; padding: 0.5rem 0.5rem 0.3rem; }
    .main-grid { gap: 3px; padding: 0.3rem 0.5rem 0.5rem; }
    .btn-fn { font-size: 0.58rem; padding: 0.4rem 0.1rem; }
    .btn-num { font-size: 0.95rem; padding: 0.7rem 0.15rem; }
    .display-result { font-size: 2rem; }
}

/* ========================================
   ACCESSIBILITÀ
   ======================================== */

@media (prefers-reduced-motion: reduce) {
    .btn { transition: none !important; }
    .btn:active { transform: none !important; }
}

.btn:focus-visible { outline: 2px solid var(--accent-color); outline-offset: 2px; }
::selection { background: var(--accent-color); color: var(--bg-color); }