:root {
    /* Richer, slightly warmer dark theme */
    --calc-body-dark: #202028;      /* Deep Black/Grey Main Body */
    --calc-body-light: #2c2c36;     /* Lighter Bezel/Accent */
    --screen-bg: #c9e6d0;           /* Authentic light green LCD background */
    --text-dark: #000;              
    --key-dark: #3a3a48;            
    --key-light: #525265;           
    --key-clear: #e74c3c;           
    --key-func-top: #444455;        
    --key-orange: #ff7f2a;          
    --shadow-color: rgba(0, 0, 0, 0.7);
    --border-radius-large: 15px;
    --border-radius-small: 8px;
}

body {
    display: flex;
    /* Changed back to column to allow credit in the header without needing a separate div footer */
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    background-color: #121215; 
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

.calculator {
    background: var(--calc-body-dark);
    padding: 25px;
    border-radius: var(--border-radius-large);
    box-shadow: 0 25px 50px var(--shadow-color), 0 0 15px rgba(255, 255, 255, 0.05);
    width: 380px; 
    user-select: none;
    border: 4px solid var(--calc-body-light);
}

/* --- Calculator Header --- */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 5px 15px 5px;
}

.logo {
    color: var(--key-orange);
    font-size: 1.3em;
    font-weight: 800;
    letter-spacing: -1px;
}

.model-name {
    /* UPDATED: Credit text color and styling */
    color: white; /* Changed color to white */
    font-size: 0.7em;
    font-weight: 500;
    letter-spacing: 1px;
}

/* --- Calculator Screen --- (remains the same) */
.screen {
    background: var(--screen-bg);
    padding: 15px 18px;
    border-radius: var(--border-radius-small);
    margin-bottom: 25px;
    height: 75px;
    text-align: right;
    overflow: hidden;
    position: relative;
    box-shadow: inset 0 2px 8px rgba(0, 0, 0, 0.2);
    border: 1px solid #8ba391;
}

.history {
    font-size: 0.9em;
    color: #333;
    min-height: 20px;
}

.main-input {
    font-size: 2.2em; 
    font-weight: 600;
    color: var(--text-dark);
    line-height: 45px;
    overflow-x: auto;
}

/* ... (Keypad and Button styles remain the same) ... */