/* Importiamo il nuovo font elegante da Google Fonts */
@import url('https://fonts.googleapis.com/css2?family=Montserrat:wght@400;600;700&display=swap');

/* =========================================
   1. RESET UNIVERSALE (Best Practice!)
   ========================================= */
*, *::before, *::after {
    box-sizing: border-box; /* Ora questa regola magica si applica a TUTTO */
}

html {
    overflow-y: auto; /* Nasconde la corsia della scrollbar su Windows se non serve */
}

/* =========================================
   2. TAVOLOZZA COLORI E VARIABILI GLOBALI
   ========================================= */
:root {
    --bg-body: #f0f3f5;        
    --bg-panel: #ffffff;       
    --primary: #2c445e;        
    --primary-hover: #e8ecf1;  
    --primary-text: #1a2838;   
    --primary-rgb: 44, 68, 94; 
    --text-main: #1e293b;      
    --text-muted: #5c6a79;     
    --border-solid: var(--primary); 
    --border-light: rgba(var(--primary-rgb), 0.2); 
    --error: #a83232;          
}

/* =========================================
   3. STILI GLOBALI E STRUTTURA
   ========================================= */
body {
    font-family: 'Montserrat', sans-serif;
    background-color: var(--bg-body); 
    color: var(--text-main); 
    display: flex;
    flex-direction: column; 
    align-items: center;
    gap: 20px; /* IL TRUCCO MAGICO: Distanzia i box solo se sono entrambi visibili! */
    padding: 40px 20px; 
    min-height: 100vh;
    margin: 0;
}

.container {
    background-color: var(--bg-panel);
    padding: 40px; 
    border-radius: 0; 
    box-shadow: 0 8px 20px rgba(var(--primary-rgb), 0.1); 
    max-width: 650px; 
    width: 100%;
    z-index: 2; 
    border: 1px solid var(--border-solid); 
    /* margin-bottom e box-sizing sono stati rimossi perché non servono più! */
}

h2 { 
    text-align: center; 
    color: var(--primary); 
    margin-bottom: 30px; 
    margin-top: 0;
    font-weight: 700;
    text-transform: uppercase; 
    letter-spacing: 1px;
}

.section { margin-bottom: 20px; }

label { 
    display: block; 
    margin-bottom: 10px; 
    font-weight: 600; 
    color: var(--text-muted); 
    font-size: 14px; 
    text-transform: uppercase; 
    letter-spacing: 0.5px; 
}

/* =========================================
   INPUT E CAMPI DI TESTO
   ========================================= */
.input-row { display: flex; gap: 20px; align-items: stretch; }
.input-row .text-field { flex-grow: 1; }
.input-row .base-field { width: 100px; text-align: center; display: flex; flex-direction: column;}

.base-display {
    background: var(--primary); 
    color: #ffffff; 
    padding: 15px 0;
    border-radius: 0; 
    font-weight: 700;
    font-size: 20px;
    border: 1px solid var(--border-solid); 
    flex-grow: 1;
    display: flex;
    align-items: center;
    justify-content: center;
}

input[type="text"] {
    width: 100%; 
    padding: 15px; 
    border: 1px solid var(--border-solid); 
    border-radius: 0; 
    font-size: 16px; 
    font-family: 'Montserrat', sans-serif;
    color: var(--text-main);
    box-sizing: border-box; 
    transition: all 0.3s;
}

input[type="text"]:focus { 
    outline: none; 
    box-shadow: 0 0 0 3px rgba(var(--primary-rgb), 0.15); 
}

#outputValue { 
    background-color: var(--primary-hover); 
    font-weight: 600; 
}

/* =========================================
   BOTTONI DELLE BASI (GRIGLIA)
   ========================================= */
.base-grid { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 20px; }

.base-grid button {
    flex: 1 1 calc(12.5% - 10px); 
    padding: 12px 0;
    background-color: var(--bg-panel); 
    border: 1px solid var(--border-solid); 
    border-radius: 0; 
    cursor: pointer;
    font-size: 14px;
    font-weight: 600;
    color: var(--primary); 
    transition: all 0.2s ease-in-out; 
}

.base-grid button:not(.active-btn):hover { 
    background-color: var(--primary-hover);
    transform: translateY(-2px); 
}

.base-grid button:active { transform: translateY(0); }

.base-grid button.active-btn { 
    background-color: var(--primary); 
    color: #ffffff; 
    cursor: default; 
}

/* =========================================
   ELEMENTI DI SERVIZIO ED ERRORI
   ========================================= */
.divider { 
    border: 0; 
    border-top: 1px dashed var(--border-solid); 
    margin: 30px 0; 
    opacity: 0.3; 
}

.error-message { 
    color: var(--error); 
    font-size: 14px; 
    min-height: 20px; 
    margin-top: 10px; 
    font-weight: 600;
}

/* =========================================
   BOTTONI DI AZIONE (IN FONDO)
   ========================================= */
.action-buttons { 
    display: flex; 
    gap: 15px; 
    margin-top: 30px; 
    border-top: 1px solid var(--border-light); 
    padding-top: 30px; 
}

.action-btn {
    flex: 1; 
    padding: 15px; 
    border: 1px solid var(--border-solid); 
    border-radius: 0; 
    font-weight: 700;
    font-family: 'Montserrat', sans-serif;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    cursor: pointer; 
    background-color: var(--bg-panel); 
    color: var(--primary); 
    transition: all 0.2s;
}

.action-btn:hover:not(:disabled) { 
    background-color: var(--primary-hover); 
}

.action-btn:disabled { 
    background-color: #f1f5f9; 
    border-color: #cbd5e1;
    cursor: not-allowed; 
    color: #94a3b8; 
}

.action-btn.active-view { 
    background-color: var(--primary); 
    color: #ffffff;
}

/* =========================================
   BOX DELLE SPIEGAZIONI
   ========================================= */
.explanation-box {
    background-color: var(--bg-panel); 
    color: var(--text-main); 
    padding: 30px; 
    border-radius: 0; 
    border: 1px solid var(--border-solid); 
    max-width: 650px; 
    width: 100%; 
    box-shadow: 0 8px 20px rgba(var(--primary-rgb), 0.1);
    display: none; 
    line-height: 1.8;
    box-sizing: border-box; 
}

.explanation-box h3 { 
    margin-top: 0; 
    color: var(--primary); 
    padding-bottom: 10px; 
    border-bottom: 1px solid var(--border-light); 
    text-transform: uppercase; 
    font-size: 16px;
}

.step { margin-bottom: 20px; }

.math-text { 
    font-family: 'Courier New', Courier, monospace; 
    background-color: var(--primary-hover); 
    padding: 4px 8px; 
    border: 1px solid rgba(var(--primary-rgb), 0.3); 
    display: inline-block; 
    margin-top: 5px; 
    color: var(--primary-text);
}

.exercise-header {
    background-color: var(--primary-hover); 
    padding: 15px; 
    font-size: 18px;
    margin-bottom: 25px; 
    text-align: center; 
    border: 1px solid var(--border-solid); 
    color: var(--primary);
    font-weight: 600;
}

/* =========================================
   REGOLE PER SMARTPHONE
   ========================================= */
@media (max-width: 600px) {
    .container, .explanation-box { padding: 20px; }
    .input-row { flex-direction: column; gap: 10px; }
    .input-row .base-field { width: 100%; flex-direction: row; align-items: center; gap: 15px; }
    label { margin-bottom: 0; }
    .base-display { padding: 10px; }
    .base-grid button { flex: 1 1 calc(25% - 10px); padding: 15px 0; }
    .action-buttons { flex-direction: column; }
}