* { 
    margin: 0; 
    padding: 0; 
    box-sizing: border-box; 
    font-family: 'Segoe UI', sans-serif; 
    transition: background 0.4s ease, transform 0.2s ease, box-shadow 0.2s ease; 
}

/* BODY & BACKGROUNDS */
body {
    background-image: url('calcbgdark.png');
    background-repeat: no-repeat;
    background-position: center;
    background-attachment: fixed;
    background-size: cover;
    background-color: #010a12;
}

body.light-mode {
    background-image: url('calcbglight.png');
    background-color: #fdfafd;
}

.container {
    width: 100%; 
    height: 100vh;
    display: flex; 
    align-items: center; 
    justify-content: center;
}

/* SIDE NAVIGATION */
.floating-nav { 
    display: flex; 
    flex-direction: column; 
    gap: 15px; 
    margin-right: 25px; 
}

.nav-circle {
    width: 50px; 
    height: 50px; 
    border-radius: 50%; 
    border: 2px solid #00d2ff;
    cursor: pointer;
    background-color: #004d73;
    color: #ffffff; 
    font-weight: bold; 
    font-size: 18px;
    box-shadow: 0 5px 10px rgba(0, 0, 0, 0.5);
}

body.light-mode .nav-circle {
    background-color: #dcd6f7;
    color: #424874;
    border: 2px solid #424874;
    box-shadow: 0 5px 10px rgba(166, 177, 225, 0.4);
}

/* CALCULATOR WRAPPER & PANELS */
.calcwrapper { 
    display: flex; 
    align-items: flex-end; 
}

.sidepanel {
    background-color: #010a12; 
    width: 0; 
    overflow: hidden;
    border-radius: 25px; 
    color: #ffffff;
    display: flex; 
    flex-direction: column; 
    opacity: 0;
    margin-bottom: 20px;
    border: 2px solid #004d73; 
}

body.light-mode .sidepanel {
    background-color: #fdfafd;
    color: #424874;
    border: 2px solid #424874; 
}

.sidepanel.active { 
    width: 400px; 
    padding: 20px; 
    opacity: 1; 
    margin: 0 15px 20px 15px; 
}

/* SCIENTIFIC HEADER SPACING */
.sidepanel h3 {
    font-size: 14px;
    text-align: center;
    margin-top: 10px;
    margin-bottom: 35px;
    letter-spacing: 3px;
}

.calculator {
    background-color: #010a12; 
    padding: 30px 25px 50px 25px;
    border-radius: 35px; 
    width: 380px;
    border: 2px solid #00d2ff; 
    box-shadow: 0 25px 60px rgba(0, 0, 0, 0.8);
    z-index: 5;
}

body.light-mode .calculator {
    background-color: #fdfafd;
    border: 2px solid #424874; 
    box-shadow: 0 25px 60px rgba(0, 0, 0, 0.8);
}

/* DISPLAY */
.display { 
    background: rgb(47, 45, 45); 
    border-radius: 20px; 
    margin-bottom: 30px; 
    padding: 20px; 
    border: 1px solid rgba(255,255,255,0.1);
}

body.light-mode .display {
    background: rgb(204, 198, 237);
    border: 1px solid #480376;
}

.display input { 
    width: 100%; border: none; background: transparent; 
    text-align: right; color: #ebeced; font-size: 38px; outline: none; 
}

body.light-mode .display input { 
    color: #1d1e1f; 
}

/* BUTTONS & 3D SHADOWS */
.buttons { display: grid; grid-template-columns: repeat(4, 1fr); gap: 15px; }

/* SCIENTIFIC GRID ADJUSTED */
.sidegrid { 
    display: grid; 
    grid-template-columns: repeat(4, 1fr); 
    gap: 12px; 
}

button {
    height: 65px; 
    border-radius: 20px; 
    border: none; 
    cursor: pointer;
    font-size: 20px; 
    position: relative;
    background-color: #2e2e2e; 
    color: #ffffff; 
    box-shadow: 0 6px 0 #000000;
}

/* SCIENTIFIC BUTTONS */
.scibtn { 
    height: 65px; 
    background-color: #003652; 
    box-shadow: 0 5px 0 #001a29; 
    font-size: 15px; 
}

.opbtn { background-color: #004d73; box-shadow: 0 6px 0 #002b40; }
.equal { background-color: #63d98d; color: #000; grid-column: span 2; box-shadow: 0 6px 0 #3e8c5a; }
.ac-btn { background-color: #4a6aa7; box-shadow: 0 6px 0 #0d2654; }
.extra { background-color: #001a29; color: #00d2ff; box-shadow: 0 6px 0 #002b40; }

/* LIGHT MODE BUTTON COLORS */
body.light-mode .numbtn { background-color: #ffffff; color: #424874; box-shadow: 0 6px 0 #b5b5b5; border: 1px solid #dcd6f7; }
body.light-mode .scibtn { background-color: #a6b1e1; color: #ffffff; box-shadow: 0 5px 0 #7e89b8; }
body.light-mode .opbtn { background-color: #dcd6f7; color: #424874; box-shadow: 0 6px 0 #b8b0d9; }
body.light-mode .equal { background-color: #b5ead7; color: #424874; box-shadow: 0 6px 0 #8ecbb5; }
body.light-mode .ac-btn, body.light-mode .extra { background-color: #c7ceea; color: #424874; box-shadow: 0 6px 0 #a5adc9; }

/* CLICK EFFECTS */
button:active {
    transform: translateY(4px);
    box-shadow: 0 2px 0 #000 !important;
}

body.light-mode button:active {
    box-shadow: 0 2px 0 #b5b5b5 !important;
}

.numbtn:active { filter: brightness(1.4); } 
body.light-mode .numbtn:active { filter: brightness(0.8); } 
.opbtn:active, .scibtn:active, .ac-btn:active { filter: brightness(0.8); } 
.equal:active { filter: brightness(1.2); box-shadow: 0 0 15px #63d98d; }
body.light-mode .equal:active { filter: brightness(0.8); box-shadow: 0 0 15px #63d98d; }

/* HISTORY */
#historycontent { flex-grow: 1; overflow-y: auto; max-height: 300px; padding: 5px; }
.history-item { padding: 10px; border-bottom: 1px solid rgba(255,255,255,0.1); cursor: pointer; }
body.light-mode .history-item { border-bottom: 1px solid #dcd6f7; }

/* Mobile Optimization */
@media (max-width: 600px) {
    .container {
        flex-direction: column; 
        height: auto;
        padding: 20px 0;
    }

    .floating-nav {
        flex-direction: row; 
        margin-right: 0;
        margin-bottom: 20px;
    }

    .calcwrapper {
        flex-direction: column;
        align-items: center;
    }

    .calculator {
        width: 90%; 
        max-width: 350px;
    }

    .sidepanel.active {
        width: 90%;
        margin: 10px 0;
    }
}