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

header {
    background: #C0DEFF;
    color: #333333;
    text-align: center;
    padding: 20px 0;
    line-height: 1.6;
}

.container {
    max-width: 960px;
    padding: 0 20px;
    margin: auto;
}

.platform-item {
    background-color: #f4f4f4;
    border-radius: 5px;
    margin: 20px 0;
    padding: 20px;
    min-width: 200px;
    text-align: center;
}

.button {
    display: block;
    padding: 16px;
    font-size: 16px;
    text-align: center;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    text-decoration: none;
}

.submit-button {
    margin: 30px auto;
    width: 100%;
    max-width: 960px;
    background: #FF5733;
}

.exchange-div {
    margin: 20px auto;
}
.exchange-input {
    width: 100%;
    margin-bottom: 10px;
    padding: 12px 10px;
    background: #fff;
    border: 1px solid #F2F2F2;
    border-radius: 5px;
    font-size: 14px;
    outline: none;
    transition: border-color 0.3s ease;
}
.exchange-input::placeholder {
    color: #AEAEAE;
}
.exchange-input:focus {
    border-color: #C0DEFF;
    color: #333;
}
.exchange-button {
    width: 100%;
    background: #C0DEFF;
    color: #333333;
    margin-bottom: 50px;
}

.footer {
    text-align: center;
    font-size: 12px;
    color: #555555;
    margin-bottom: 50px;
}

@media (max-width: 768px) {
    .platform-item {flex: 1 1 calc(50% - 20px);}
}

@media (max-width: 480px) {
    .platform-item {flex: 1 1 100%;}
}