.container {
    width: 350px;
    height: 500px;
    background: #333;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 20px auto;
    position: relative;

}

.signin-signup {
    display: grid;
    grid-template-columns: 1fr;content: center;
}

form {
    grid-column: 1 / 2;
    grid-row: 1/2;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
}

form.sign-up-form {
    visibility: hidden;
}

.title {
    font-size: 35px;
    color: #999;
    margin-bottom: 10px;
}

.input-field {
    width: 280px;
    height: 50px;
    border-bottom: 2px solid #999;
    margin: 10px 0;
    display: flex;
    align-items: center;
}

.input-field i {
    flex: 1;
    text-align: center;
    font-size: 20px;
    color: #999;
}

.input-field input {
    flex: 5;
    border: none;
    outline: none;
    background: none;
    font-size: 18px;
    color: #f0f0f0;
    font-weight: 600;

}

.forgot-password {
    align-self: flex-end;
}

.btn {
    width: 130px;
    height: 40px;
    background: none;
    outline: none;
    border: 2px solid #999;
    text-transform: uppercase;
    font-size: 18px;
    font-weight: 600;
    margin: 20px 0;
    color: #999;
}

.btn:hover {
    color: #333;
    border: none;
    background: #999;
}

.container.sign-up-mode form.sign-up-form {
    visibility: visible;
}

.container.sign-up-mode form.sign-in-form {
    visibility: hidden;
}

@media (max-width: 400px) {
    .container {
        width: 100vw;
        height: 100vh;
    }
}