* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: Arial, sans-serif;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #1a1a1a;
}

.calculator-container {
    background-color: #2d2d2d;
    border-radius: 20px;
    padding: 20px;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.3);
    width: 90%;
    max-width: 350px;
    margin: 20px;
}

.mode-switch {
    display: flex;
    gap: 10px;
    margin-bottom: 15px;
}

.mode-switch button {
    flex: 1;
    padding: 8px;
    border: none;
    border-radius: 8px;
    background-color: #3d3d3d;
    color: #fff;
    cursor: pointer;
    transition: 0.3s;
}

.mode-switch button.active {
    background-color: #ffd700;
    color: #000;
}

.display {
    background-color: #1a1a1a;
    padding: 20px;
    border-radius: 10px;
    margin-bottom: 15px;
}

#history {
    min-height: 20px;
    color: #888;
    font-size: 14px;
    text-align: right;
    margin-bottom: 5px;
}

#result {
    color: #fff;
    font-size: 32px;
    text-align: right;
}

.notes {
    margin-bottom: 15px;
}

#calcNotes {
    width: 100%;
    height: 60px;
    background-color: #1a1a1a;
    border: none;
    border-radius: 10px;
    padding: 10px;
    color: #fff;
    resize: none;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

.buttons button {
    padding: clamp(10px, 3vw, 15px);
    border: none;
    border-radius: 10px;
    font-size: clamp(16px, 4vw, 18px);
    cursor: pointer;
    background-color: #3d3d3d;
    color: #fff;
    transition: 0.3s;
    width: 100%;
    height: 100%;
}

.buttons button:hover {
    background-color: #4d4d4d;
}

.buttons button.operator {
    background-color: #2d2d2d;
}

.buttons button.equals {
    background-color: #ffd700;
    color: #000;
    grid-column: span 2;
}

.buttons button.equals:hover {
    background-color: #ffed4a;
}

.hidden {
    display: none;
}

@media screen and (max-width: 480px) {
    .calculator-container {
        padding: 15px;
    }

    .buttons {
        gap: 5px;
    }

    #result {
        font-size: 28px;
    }

    #history {
        font-size: 12px;
    }

    #calcNotes {
        height: 50px;
    }

    .mode-switch button {
        padding: 6px;
        font-size: 14px;
    }
}

@media screen and (max-width: 320px) {
    .calculator-container {
        padding: 10px;
    }

    .buttons {
        gap: 4px;
    }

    #result {
        font-size: 24px;
    }

    .buttons button {
        font-size: 14px;
        padding: 8px;
    }
}

@media screen and (max-height: 600px) {
    .calculator-container {
        margin: 10px;
    }

    #calcNotes {
        height: 40px;
    }

    .display {
        padding: 10px;
    }
}

.login-container {
    background-color: #2d2d2d;
    border-radius: 20px;
    padding: 20px;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.3);
    width: 90%;
    max-width: 300px;
    margin: 20px auto;
    text-align: center;
}

.login-container h2 {
    color: #ffd700;
    margin-bottom: 20px;
}

.login-container input {
    width: 100%;
    padding: 10px;
    margin-bottom: 10px;
    border: none;
    border-radius: 5px;
    background-color: #1a1a1a;
    color: #fff;
}

.login-container button {
    width: 100%;
    padding: 10px;
    border: none;
    border-radius: 5px;
    background-color: #ffd700;
    color: #000;
    cursor: pointer;
    transition: 0.3s;
}

.login-container button:hover {
    background-color: #ffed4a;
}

.error-message {
    color: red;
    margin-top: 10px;
}

.user-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
    color: #fff;
}

.logout-btn {
    padding: 5px 10px;
    border: none;
    border-radius: 5px;
    background-color: #ff4444;
    color: white;
    cursor: pointer;
    transition: 0.3s;
}

.logout-btn:hover {
    background-color: #ff6666;
}

.form-toggle {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

.form-toggle button {
    flex: 1;
    padding: 8px;
    border: none;
    border-radius: 5px;
    background-color: #3d3d3d;
    color: #fff;
    cursor: pointer;
    transition: 0.3s;
}

.form-toggle button.active {
    background-color: #ffd700;
    color: #000;
}

.form-section {
    transition: 0.3s;
}

.form-section.hidden {
    display: none;
}

.login-container input {
    margin-bottom: 15px;
}

.login-container h2 {
    margin-bottom: 20px;
}